Chapter 5 PHP Array Operation_PHP Tutorial-PHP Tutorial-php.cn

one. What is an array
An array is a set of elements that share certain characteristics, including similarity and type.
Each element is distinguished by a special identifier, called a key, and each key has a value
1. Two ways to create an array:
1.1 Use the array() function

Copy code The code is as follows:

 
$usernames = array ('Alerk', 'Mary' , 'Lucy', 'Bob', 'Jack', 'John', 'Mark' ); 
foreach ( $usernames as $name ) 
{ 
echo $name . '
} 
?> 

output
Alerk
Mary
Lucy
Bob
Jack
John
Mark
1.2 Use range() function

Copy code The code is as follows:

 
$ numbers = range ( 0, 10 ); 
foreach ( $numbers as $num ) 
{ 
echo $num . '
'; 
} 
$letters = range ( 'a', 'z' ); 
foreach ( $letters as $letter ) 
{ 
echo $letter . '
'; 
} 
? > 

output
0
1
2
3
4
5
6
7
8
9
10
a

c
d
e
f
g
h
i
j
k
l
m

o

q
r

t
u
v
w
x
y
z
2. Two ways to loop through array elements:
2.1 for loop

Copy code The code is as follows:

 
//The third parameter of range represents the step size
$numbers = range(1,10,2); 
for($i = 0 ;$i{ 
echo $numbers[$i].'
'; 
} 
?> 

output
1
3
5
7
9
2.2 foreach loop

Copy code The code is as follows:

 
$letters = range('a','h',2); 
foreach($letters as $letter ) 
{ 
echo $letter.'
'; 
} 
?> 

output
a
c
e
g
Foreach can also be used to output the subscript and corresponding value of the array

Copy code The code is as follows:

 
$letters = range('a','g',2); 
foreach($letters as $key => $value) 
{ 
echo $key.'---'.$value.'
'; 
} 
?> 

output
0-- -a
1---c
2---e
3---g
3.is_array() function, used to determine whether the variable is an array

Copy code The code is as follows:

 
$numbers = range(1,10,2); 
if( is_array($numbers)) 
{ 
foreach($numbers as $num) 
{ 
echo $num.'
'; 
} 
} 
else 
{ 
echo $numbers; 
} 
?> 

4.print_r function, prints easy-to-understand information about variables

Copy code The code is as follows:

 
$usernames = array ('Jackie', 'Mary', 'Lucy ', 'Bob', 'Mark', 'John' ); 
print_r ( $usernames ); 
?> 

output
Array ( [0] => ; Jackie [1] => Mary [2] => Lucy [3] => Bob [4] => Mark [5] => John )
The source code can be seen as:
Array
(
[0] => Jackie
[1] => Mary
[2] => Lucy
[3] => Bob
[4] => Mark
[5] => John
)
2. Custom key array
1. If you don’t want to create an array with the default subscript zero, you can use the following method to create an array with keys as strings

Copy code The code is as follows:

 
//Initialize array
$userages = array('Jack'=> 23,'Lucy'=>25,' Mark'=>28); 
//Accessing each element of the array
echo $userages['Jack'].'
'; 
echo $userages['Lucy']. '
'; 
echo $userages['Mark'].'
'; 
?> 

2. Go to Customize Append elements to the key array

Copy code The code is as follows:

 
//Initialize array
$ages = array('Jack'=>23); 
//Append elements
$ages['Lucy' ]=25; 
$ages['Mark']=28; 
foreach($ages as $key => $value) 
{ 
echo $key.'----' .$value.'
'; 
} 
?> 

3. Add elements directly without creating an array.

Copy code The code is as follows:

 
//Add directly without creating an array
$ ages['Jack']=23; 
$ages['Lucy']=25; 
$ages['Mark']=28; 
foreach($ages as $key => $value ) 
{ 
echo $key.'----'.$value.'
'; 
} 
?> 

4. Use of loop printing array foreach

Copy code The code is as follows:

 
$ages[ 'Jack']=23; 
$ages['Lucy']=25; 
$ages['Mark']=28; 
foreach($ages as $key => $value) 
{ 
echo $key.'=>'.$value.'
'; 
} 
?> 

5. each () -- Returns the current key/value pair in the array and moves the array pointer forward one step

Copy code The code is as follows:

 
$ages['Jack']=23; 
$ages['Lucy']=25; 
$ages['Mark']=28; 
$ a = each($ages); 
print_r($a); 
echo '
'; 
$a = each($ages); 
print_r($a) ; 
echo '
'; 
$a = each($ages); 
print_r($a); 
?> 

Use each() function to do loop printing

Copy code The code is as follows:

 
$ages[ 'Jack']=23; 
$ages['Lucy']=25; 
$ages['Mark']=28; 
while(!! ​​$element = each($ages)) 
{ 
print_r($element); 
echo '
'; 
} 
?> 

Another printing method

Copy code The code is as follows:

 
$ages['Jack']=23; 
$ ages['Lucy']=25; 
$ages['Mark']=28; 
while(!! ​​$element = each($ages)) 
{ 
echo $element[' key'].'=>'.$element['value']; 
echo '
'; 
} 
?> 

6. Use of the list() function - assign the values in the array to some variables

Copy the code The code is as follows:

 
< ;?php 
$ages['Jack']=23; 
$ages['Lucy']=25; 
$ages['Mark']=28; 
list($name, $age)= each($ages); 
echo $name.'=>'.$age; 
?> 

Use list loop to print the results

Copy code The code is as follows:

 
$ages['Jack']=23; 
$ages ['Lucy']=25; 
$ages['Mark']=28; 
while(!!list($name,$age)= each($ages)) 
{ 
 echo $name.'=>'.$age.'
'; 
} 
?> 

output
Jack=>23
Lucy=>25
Mark=>28
7. Use of reset() function--point the internal pointer of the array to the first unit

Copy Code The code is as follows:

 
$ages['Jack']=23; 
$ages['Lucy']=25; 
$ages['Mark']=28; 
each($ages); 
each($ages); 
list($name,$age)= each($ages); 
echo $name.'=>'.$age.'
'; 
//Reset the array to the beginning of the array
reset($ages); 
list($ name,$age)= each($ages); 
echo $name.'=>'.$age.'
'; 
?> 

Output
Mark=>28
Jack=>23
8. array_unique() -- Remove duplicate values in the array

Copy code The code is as follows:

 
$nums = array(1,2,3,4,5,6,5,4,3,2,1, 1,2,3,4,5,6); 
//Return an array that does not contain duplicate values
$result = array_unique($nums); 
print_r($result); 
 ?> 
Output 
Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 [5] => 6 ) 
9. array_flip ()-- Swap the keys and values ​​in the array 
$userages = array('Jack'=> 23,'Lucy'=> ;25,'Mark'=>28); 
$ages = array_flip($userages); 
print_r($ages); 
?> 

output
Array ( [23] => Jack [25] => Lucy [28] => Mark )
3. The array
in the array is not necessarily a list of keywords and values. You can also put the array

in the array. Copy the code . The code is as follows:

 
$produces = array( 
array('apple',6,28.8), 
array('pear',3,15.6), 
array('banana',10,4.6) 
); 
echo $produces[0][0].'|'.$produces[0][1].'|'.$produces[ 0][2].'
'; 
echo $produces[1][0].'|'.$produces[1][1].'|'.$produces[1][2 ].'
'; 
echo $produces[2][0].'|'.$produces[2][1].'|'.$produces[2][2].'< ;br>'; 
?> 

output
apple|6|28.8
pear|3|15.6
banana|10|4.6
Use for Loop to print the array within the array

Copy code The code is as follows:

 
$produces = array ( 
array ('apple', 6, 28.8 ), 
array ('pear', 3, 15.6 ), 
array ('banana', 10, 4.6 ) 
); 
for ($i = 0; $i < count ( $produces ); $i ++) 
{ 
for($j = 0; $j < count ( $produces [$i] ); $ j ++) 
{ 
echo '|' . $produces[$i][$j]; 
} 
echo '
'; 
} 
? > 

output
|apple|6|28.8
|pear|3|15.6
|banana|10|4.6
Two-dimensional array

Copy code The code is as follows:

 
$produces = array ( 
array ('name' => 'apple', 'amount' => 6, 'price' => 28.8 ), 
array ('name' => 'pear', 'amount' => 3, 'price' => 15.6 ), 
array ('name' => 'banana', 'amount' => 10, 'price' => 4.6 ) 
); 
while(!!List($key ,$value)=each($produces)) 
{ 
while(!!list($key2,$value2)=each($value)) 
{ 
echo '|'.$ key2.'=>'.$value2; 
} 
echo '
'; 
} 
?> 

Copy the code The code is as follows:

 
$produces = array ( 
array ('name' => 'apple', 'amount' => 6, 'price' => 28.8 ), 
array ('name' => 'pear', 'amount' => 3, 'price' => 15.6 ), 
array ('name' => 'banana', 'amount' => ; 10, 'price' => 4.6 ) 
); 
foreach($produces as $key1 => $value1) 
{ 
foreach($value1 as $key2 => $ value2) 
{ 
echo '|'.$key2.'=>'.$value2; 
} 
echo '
'; 
} 
?> ; 

Copy code The code is as follows:

 
< meta http-equiv="content-type" content="text/html;charset=utf-8" /> 
$fruits = array('lemo','banana',' apple','pear'); 
echo 'Original array:'; 
print_r($fruits); 
echo '
'; 
sort($fruits); 
echo 'Sorted array:'; 
print_r($fruits); 
?> 

output
Original array: Array ( [0] = > lemo [1] => banana [2] => apple [3] => pear )
Sorted array: Array ( [0] => apple [1] => banana [ 2] => lemo [3] => pear )
2.Sort() function to sort Chinese

Copy code The code is as follows:

 
 
$fruits = array('lemon','banana','apple','pear'); 
echo 'Original array:'; 
print_r($fruits); 
echo '
 '; 
sort($fruits); 
echo 'Sorted array:'; 
print_r($fruits); 
?> 

Output:
Original array: Array ([0] => lemon[1] => banana[2] => apple[3] => pear)
sorted array :Array ([0] => Lemon[1] => Pear[2] => Apple[3] => Banana)
3. asort -- Sort the array and maintain the index relationship

Copy code The code is as follows:

 
 
$fruits = array('a'=>'Lemon','b'=>'Banana','c'=>' Apple','d'=>'Pear'); 
echo 'Original array:'; 
print_r($fruits); 
echo '
'; 
 asort($fruits); 
echo 'Sorted array:'; 
print_r($fruits); 
?> 

output
Original array: Array ([a] => lemon[b] => banana[c] => apple[d] => pear)
Sorted array: Array ([a] => lemon[d] ] => Pear[c] => Apple[b] => Banana)
4. ksort -- Sort the array by key name

Copy code The code is as follows:

 
 
$fruits = array('b'=>'Lemon','a'=>'Banana','d'=>'Apple','c'=>'Pear'); 
echo 'Original array:'; 
print_r($fruits); 
echo '
'; 
ksort($fruits); 
echo 'Sorted Array: '; 
print_r($fruits); 
?> 

output
Original array: Array ([b] => lemon[a] => ; Banana[d] => Apple[c] => Pear)
Sorted array: Array ( [a] => Banana[b] => Lemon[c] => Pear[d ] => Apple)
5. rsort -- Reverse sort the array

Copy code The code is as follows:

 
  
$fruits = array('Lemon','Banana' ,'apple','pear'); 
echo 'Original array:'; 
print_r($fruits); 
echo '
'; 
rsort($fruits ); 
echo 'Sorted array:'; 
print_r($fruits); 
?> 

output
Original array: Array ( [0 ] => Lemon[1] => Banana[2] => Apple[3] => Pear)
Sorted array: Array ( [0] => Banana[1] => Apple[2] => Pear[3] => Lemon)
6. arsort -- Sort the array in reverse and maintain the index relationship

Copy code The code is as follows:

 
 
$fruits = array('a'=>'Lemon','b'=>'Banana','c'=>'Apple','d'=>'Pear'); 
echo 'Original array:'; 
print_r($fruits); 
echo '
'; 
arsort($fruits); 
echo 'Sorted array ：'; 
print_r($fruits); 
?> 

output
Original array: Array ([a] => Lemon[b] => Banana[c] => Apple[d] => Pear)
Sorted array: Array ( [b] => Banana[c] => Apple[d] => Pear[a] => Lemon)
7. krsort -- Sort the array in reverse order by key name

Copy the code The code is as follows:

 
 
$fruits = array('a'=> ;'Lemon','b'=>'Banana','c'=>'Apple','d'=>'Pear'); 
echo 'Original array:'; 
 print_r($fruits); 
echo '
'; 
krsort($fruits); 
echo 'Sorted array:'; 
print_r($fruits); 
?> 

output
Original array: Array ([a] => lemon[b] => banana[c] => apple[d] => ; Pear)
Sorted array: Array ( [d] => Pear[c] => Apple[b] => Banana[a] => Lemon)
8. shuffle -- Shuffle the array

Copy the code The code is as follows:

 
 
$fruits = array(' a'=>'Lemon','b'=>'Banana','c'=>'Apple','d'=>'Pear'); 
echo 'Original array:' ; 
print_r($fruits); 
echo '
'; 
shuffle($fruits); 
echo 'Shuffled array:'; 
print_r( $fruits); 
?> 

output
Original array: Array ( [a] => Lemon[b] => Banana[c] => Apple [d] => Pear)
Shuffled array: Array ( [0] => Banana[1] => Apple[2] => Lemon[3] => Pear)
9. array_reverse -- Returns an array with the cells in reverse order

Copy code The code is as follows:

 
 
$fruits = array('a'=>'Lemon','b '=>'Banana','c'=>'Apple','d'=>'Pear'); 
echo 'Original array:'; 
print_r($fruits); 
echo '
'; 
$fruits = array_reverse($fruits); 
echo 'Reversed array:'; 
print_r($fruits); 
? > 

output
Original array: Array ([a] => lemon[b] => banana[c] => apple[d] => pear)
Reversed array: Array ([d] => Pear[c] => Apple[b] => Banana[a] => Lemon)
10. array_unshift -- in array Insert one or more units at the beginning

Copy code The code is as follows:

 
 
$fruits = array('a'=>'Lemon','b'=>'Banana ','c'=>'Apple','d'=>'Pear'); 
echo 'Original array:'; 
print_r($fruits); 
echo '< br/>'; 
array_unshift($fruits,'杮子'); 
echo 'Array after insertion:'; 
print_r($fruits); 
?> 
 

output
Original array: Array ([a] => Lemon[b] => Banana[c] => Apple[d] => Pear)
After insertion Array: Array ([0] => 杮子[a] => lemon[b] => banana[c] => apple[d] => pear)
11. array_shift -- Move the unit at the beginning of the array out of the array

Copy code The code is as follows:

 
 
$fruits = array('a'=>'Lemon','b'=>'Banana ','c'=>'Apple','d'=>'Pear'); 
echo 'Original array:'; 
print_r($fruits); 
echo '< br/>'; 
array_shift($fruits); 
echo 'Array after shifting:'; 
print_r($fruits); 
?> 

output
Original array: Array ([a] => lemon[b] => banana[c] => apple[d] => pear)
The moved array: Array ( [b] => Banana [c] => Apple [d] => Pear)
12. array_rand -- Randomly remove one or more units from the array

Copy code The code is as follows:

 
 
$fruits = array ('Lemon', 'Banana', 'Apple', 'Pear' ); 
echo 'Original array:'; 
print_r ( $fruits ); 
echo '
'; 
$newArr_key = array_rand ( $fruits, 2 ); 
echo 'Array after randomization:'; 
echo $fruits [$newArr_key [0]].' '; 
echo $fruits [$newArr_key [1]]; 
?> 

output
Original array: Array ( [0] => Lemon[1] => Banana[2] => Apple[3] => Pear)
Random array: pear apple
13. array_pop -- Pop the last unit of the array (Pop)

Copy code The code is as follows:

 
 
$fruits = array ('lemon', 'banana', 'apple', 'pear' ); 
echo 'Original array:'; 
print_r ( $fruits ); 
echo '
'; 
array_pop ( $fruits ); 
echo 'Array after popping:'; 
print_r ( $fruits ); 
?> 

Output:
Original array: Array ([0] => Lemon[1] => Banana[2] => Apple[3] => Pear)
Array after popping :Array ([0] => Lemon[1] => Banana[2] => Apple)
14. array_push -- Push one or more cells to the end of the array (push)

Copy code The code is as follows:

 
 
$fruits = array ('Lemon', 'Banana', 'Apple', 'Pear' ); 
echo 'Original array:' ; 
print_r ( $fruits ); 
echo '
'; 
array_push ( $fruits,'杮子'); 
echo 'Array after popping:'; 
print_r ( $fruits ); 
?> 

Output:
Original array: Array ( [0] => Lemon[1] => Banana[2 ] => Apple[3] => Pear)
Array after popping up: Array ([0] => Lemon[1] => Banana[2] => Apple[3] => Pear[4] => 杮子)
5. Array pointer operations
each -- Returns the current key/value pair in the array and moves the array pointer forward one step
current -- Returns the current unit in the array
reset -- Moves the internals of the array The pointer points to the first unit
end -- points the internal pointer of the array to the last unit
next -- moves the internal pointer in the array forward one bit
pos -- alias of current()
prev -- Rewind the internal pointer of the array by one bit

Copy code The code is as follows:

 
$fruits = array ('lemons', 'banana', 'apple' , 'Pear' ); 
print_r ( $fruits ); 
echo '
'; 
echo 'each() : '; 
print_r ( each ( $fruits ) ) ; 
echo '
'; 
echo 'current() : '; 
echo (current ( $fruits )); 
echo '
'; 
echo 'next() : '; 
echo (next ( $fruits )); 
echo '
'; 
echo 'end() : '; 
 echo (end ( $fruits )); 
echo '
'; 
echo 'prev() : '; 
echo (prev ( $fruits )); 
echo ' 
'; 
echo 'pos() : '; 
echo (pos ( $fruits )); 
echo '
'; 
?> 

Output:
Array ( [0] => Lemon[1] => Banana[2] => Apple[3] => Pear)
each( ) : Array ( [1] => lemon[value] => lemon[0] => 0 [key] => 0 )
current() : banana
next() : apple
end() : Pear
prev() : Apple
pos() : Apple
6. Count the number of arrays
count -- Count the number of cells in the array or the number of attributes in the object
sizeof -- Alias of count()
array_count_values -- Count the number of occurrences of all values in the array

Copy code The code is as follows:

 
$nums = array (1, 3, 5, 1 , 3, 4, 5, 65, 4, 2, 2, 1, 4, 4, 1, 1, 4, 1, 5, 4, 5, 4 ); 
echo count ( $nums ); 
echo '
'; 
echo sizeof ( $nums ); 
echo '
'; 
$arrayCount = array_count_values ​​( $nums ); 
print_r ( $arrayCount ) ; 
?> 

output
22
22
Array ( [1] => 6 [3] => 2 [5] => 4 [4] => 7 [65] => 1 [2] => 2 )
Seven. Convert the array into a scalar variable: extract()
Convert each element in the array into a variable. The variable name is the key of the array element, and the variable value is the value of the array element.

Copy code The code is as follows:

 
$fruits = array('a'=>'apple','b'=> 'banana','o'=>'orange'); 
extract($fruits); 
echo $a.'
'; 
echo $b.'
 '; 
echo $o.'
'; 
?> 

output
apple
banana
orange