PHP array usage skills and operation summary

Arrays can be said to be the most important method in PHP data applications. There are many array functions in PHP. Here are some summaries to remember them for future reference.

1. Array definition
Use of array definition Defined in array() method, you can define an empty array:
$number = array(1,3,5,7,9);
//Define an empty array
$result = array();
$color =array("red","blue","green");
//Custom key value
$language = (1=>"English",3=>"Chinese",5=>"Franch");
//Define a two-dimensional array
$two = array(
"color"=>array("red","blue"), //end with comma
"week"=>array("Monday","Friday") //The last sentence has no punctuation
);
?>

2. Create array
compact()
compact() function - Convert one or more variables (including arrays) to an array: array compact ( mixed $varname [, mixed $... ] ).
$number = "1,3,5,7,9";
$string = "I'm PHPer";
$array = array("And","You?");
$newArray = compact("number","string","array");
print_r ($newArray);
?>
compact() function is used to convert two or more variables into arrays, including array variables of course. The parameter is the name of the variable rather than the full name with $. The opposite function is extract(). As the name suggests, it converts the array into a single string, with the key value as its string name and the array value as the string value.
Run result:

Array (
[number] => 1,3,5,7,9
[string] => I'm PHPer
[array] => Array ( [0] => And [1] => You? )
)
array_combine()
array_combine() - Reorganize two arrays into one array, one as the key value and the other as the value: array array_combine (array $keys , array $values ​​)
$number = array("1","3","5","7","9");
$array = array("I","Am","A","PHP","er");
$newArray = array_combine($number,$array);
print_r ($newArray);
?>
I won’t say much about the array_combine function, everyone will understand it after reading it.
Run result:
Array ( [1] => I [3] => Am [5] => A [7] => PHP [9] => er )
range()
range() function - creates an array of a specified range:
$array1 = range(0,100,10);//0 is the starting value, 100 is the end value, and 10 is the step value (the default step value is 1).
print_r($array1);
echo"
";
$array2 = range("A","Z");
print_r($array2);
echo "
";
$array3 = range("z","a");
print_r($array3);
?>
array_fill()
array_fill() function - fill array function:
$array = range(1,10);
$fillarray = range("a","d");
$arrayFilled = array_fill(0,5,$fillarray);//$fillarray here can be a string, such as "test".
echo "

"; <br>print_r ($arrayFilled); <br>echo "

";
$keys = array("string","2",9,"SDK","PK");
$array2 = array_fill_keys($keys,"testing");
echo "

"; <br>print_r ($array2);
<br>echo "

";
?>
Run result:
Array
(
[0] => Array
(
[0] => a
[1] => b
[2] => c
[3] => d
)

[1] => Array
(
[0] => a
[1] => b
[2] => c
[3] => d
)

[2] => Array
(
[0] => a
[1] => b
[2] => c
[3] => d
)

[3] => Array
(
[0] => a
[1] => b
[2] => c
[3] => d
)

[4] => Array
(
[0] => a
[1] => b
[2] => c
[3] => d
)

)
Array
(
[string] => testing
[2] => testing
[9] => testing
[SDK] => testing
[PK] => testing
)

3. Array traversal
foreach traversal
foreach (array_expression as $value){}
foreach (array_expression as $key => $value){}

$speed = array(50,120,180,240,380);
foreach($speed as $keys=>$values){
echo $keys."=>".$values."
";
}
?>
Run result:
0=>50
1=>120
2=>180
3=>240
4=>380
while loop traversal
While loop traversal is generally combined with the list function. The following is an example
$staff = array(
array("Name","Gender","Age"),
array("Xiao Zhang","Male",24),
array("Xiao Wang","Female",25),
array("Xiao Li","Male",23)
);
echo "

";
while(list($keys,$value) = each($staff)){
list($name,$sex,$age) = $value;
echo "";
}
echo "

$name

$sex

$age

";
?>
for loop traversal
$speed = range(0,220,20);
for($i =0;$iecho $speed[$i]." ";
}
?>
Operating results:
0 20 40 60 80 100 120 140 160 180 200 220
4. Array pointer operations
Involved functions include reset, prev, end, next, current, and each.
Example 1: next and prev
$speed = range(0,220,20);
echo current($speed);//Output the value of the current position (at the beginning of the array)
$i = rand(1,11);
while($i--){
next($speed);//Move the pointer one position backward from the current position
}
echo current($speed);//Output the value of the current position
echo "
";
echo prev($speed);//Output the previous position array value
echo "
";
echo reset($speed);//Reset the pointer of the array and point the pointer to the starting position
echo "
";
echo end($speed);//Output the array value of the last position
echo "
";
?>
Run result:
0220
200
0
220
Example 2: each function pointer operation
$speed = range(0,200,40);
echo "each moves the pointer down
";
echo "The speed of 0 gear is".current(each($speed))."
";
echo "The speed of 1st gear is".current(each($speed))."
";
echo "The speed of 2nd gear is".current(each($speed))."
";
echo "The speed of 3rd gear is".current(each($speed))."
";
echo "The speed of 4th gear is".current(each($speed))."
";
echo "The speed of 5th gear is".current(each($speed))."
";
echo "Use each function to move the array pointer and perform array traversal
";
reset($speed);//Here, the array pointer points to the beginning of the array
while(list($key,$value)=each($speed)){
echo $key."=>".$value."
";
}
?>
Operating results:
each realizes the pointer moving down
The speed of 0 gear is 0
The speed of 1st gear is 40
The speed of 2nd gear is 80
The speed of 3rd gear is 120
The speed of 4th gear is 160
The speed of 5th gear is 200
Use each function to move the array pointer and traverse the array
0=>0
1=>40
2=>80
3=>120
4=>160
5=>200
5. Array addition and deletion operations

Add array members
Example 1: $num[] = Value is directly assigned and appended to the end of the array:
[code]$num = array(1=>80,2=>120,3=>160);
echo "Use expressions to add array members
";
$num[]=240;
print_r($num);
?>

Run result:
Use expression to add array members
Array ( [0] => 80 [1] => 120 [2] => 160 [3] => 240 )
Example 2: array_pad function, selective appending of the beginning and end of an array

$num = array(1=>80,2=>120,3=>160);
$num = array_pad($num,4,200);
echo "Use the array_pad function to add members to the end of the array
";
print_r($num);
echo "
array_pad can also fill the head of the array
";
$num = array_pad($num,-8,40);
print_r($num);
?>

Run results:
Use the array_pad function to add members to the end of the array
Array ( [0] => 80 [1] => 120 [2] => 160 [3] => 200 )
array_pad can also fill the head of the array
Array ( [0] => 40 [1] => 40 [2] => 40 [3] => 40 [4] => 80 [5] => 120 [6] => 160 [7] => 200 )
Example 3: Push operation append (array_push):
$num = array(1=>80,2=>120,3=>160);
array_push($num,200,240,280);//You can add it yourself, directly at the end of the array
print_r($num);
?>

Run result:
Array ( [1] => 80 [2] => 120 [3] => 160 [4] => 200 [5] => 240 [6] => 280 )
Example 4: array_unshift() adds array members at the beginning

$num = array(1=>80,2=>120,3=>160);
array_unshift($num,0,40);//You can add it yourself, directly at the end of the array
print_r($num);
?>

Run result:
Array ( [0] => 0 [1] => 40 [2] => 80 [3] => 120 [4] => 160 )
Note: After using the array_unshift() function, the key value of the array will start from 0!
Delete array members
Example 1: The unset() command deletes array members or arrays:
Copy the code The code is as follows:$num = array_fill(0,5,rand(1,10));
print_r($num);
echo "
";
unset($num[4]);
print_r($num);
echo "
";
unset($num);
if(is_array){
echo "The unset command cannot delete the entire array";
}else{
echo "The unset command can delete an array";
}
?>

Run result: (Running error and description array are also deleted and no longer exist)
Array ( [0] => 9 [1] => 9 [2] => 9 [3] => 9 [4] => 9 )
Array ( [0] => 9 [1] => 9 [2] => 9 [3] => 9 )

Notice: Use of undefined constant is_array - assumed 'is_array' in H:wampwwwtestingeditorplustest.php on line 21
The unset command cannot delete the entire array
Example 2: array_splice() function deletes array members
$a=array("red", "green", "blue", "yellow");
count ($a); //get 4
array_splice($a,1,1); //Delete the second element
count ($a); //Get 3
echo $a[2]; //Get yellow
echo $a[1]; //Get blue
?>

Example 3: array_unique deletes duplicate values ​​in the array:

$a=array("red", "green", "blue", "yellow","blue","green");
$result = array_unique($a);
print_r($result);
?>
Run result:
Array ( [0] => red [1] => green [2] => blue [3] => yellow )
Example 4: array_merge, array_merge_recursive merge arrays
$array1 = array("r"=>"red",1,2,3,4);
$array2 = array("b"=>"blue",4=>5,6,7,8,9);
$array3 = array("r"=>"read",4=>10,2=>11);
$array4 = array(
array(4=>10),
array(7=>13)
);
$array5 = array(
array(4=>11),
array(6=>12)
);
$result = array_merge($array1,$array2,$array3,$array4,$array5);
echo "

";
<br>print_r($result); <br>echo "

";
$result = array_merge_recursive($array1,$array2,$array3,$array4,$array5);
echo "

"; <br>print_r ($result); <br>echo "

";
?>
Array
(
[r] => read
[0] => 1
[1] => 2
[2] => 3
[3] => 4
[b] => blue
[4] => 5
[5] => 6
[6] => 7
[7] => 8
[8] => 9
[9] => 10
[10] => 11
[11] => Array
(
[4] => 10
)

[12] => Array
(
[7] => 13
)

[13] => Array
(
[4] => 11
)

[14] => Array
(
[6] => 12
)

)
Array
(
[r] => Array
(
[0] => red
[1] => read
)

[0] => 1
[1] => 2
[2] => 3
[3] => 4
[b] => blue
[4] => 5
[5] => 6
[6] => 7
[7] => 8
[8] => 9
[9] => 10
[10] => 11
[11] => Array
(
[4] => 10
)

[12] => Array
(
[7] => 13
)

[13] => Array
(
[4] => 11
)

[14] => Array
(
[6] => 12
)

)
Note: 1. If the key name of array_merge is numeric, the index will be re-established; when the same string key name is encountered, the later one will overwrite the previous one. 2. The function of array_merge_recursive function is to integrate the key name units of the same string into an array.
6. Array key and value operations
Example 1: in_array() detects whether a certain value exists in the array

$array = range(0,9);
if(in_array(9,$array)){
echo "Exists in array";
}
?>
Run result: Exists in array

Example 2: key() gets the current key name of the array:

$array = range(0,9);
$num = rand(0,8);
while($num--)
next($array);
$key = key($array);
echo $key;
?>
The result of this example is a dynamic result, the range is (0-8), and no result demonstration is performed.

Example 3: The list() function assigns the values ​​in the array to the specified variable:
array("Xiao Li","Male",23)
);
echo "

";
while(list($keys,$value) = each($staff)){
list($name,$sex,$age) = $value;
echo "";
}
echo "

$name

$sex

$age

";
?>

Example 4: array_flip() exchanges the key and value of the array:

$array = array("red","blue","yellow","Black");
print_r($array);
echo "
";
$array = array_flip($array);
print_r($array);
?>

Run result:
Array ([0] => red [1] => blue [2] => yellow [3] => Black )
Array ( [red] => 0 [blue] => 1 [yellow] => 2 [Black] => 3 )

$array = array("red","blue","yellow","Black");
$result = array_keys($array);
print_r($result);
echo "
";
$result = array_values($array);
print_r($result);
?>

Run result:
Array ( [0] => 0 [1] => 1 [2] => 2 [3] => 3 )
Array ( [0] => red [1] => blue [2] => yellow [3] => Black )
Example 6: array_search() search value:

$array = array("red","blue","yellow","Black");
$result = array_search("red",$array);
if(($result === NULL)){
echo "The value red does not exist";
}else{
echo "The value red exists $result";
}
?>

Result: Value 0 exists
The value returned by the function array_search() may be false or 0 or NULL, so be careful to use "===" when making judgments
7. Sorting of arrays
Example 1: sort(), rsort()/asort(), arsort() to sort arrays:

$array = array("b","c","d","a");
sort($array);//Sort from low to high
print_r($array);
echo "
";
rsort($array);//Reverse sort
print_r($array);
?>

Result:
Array ([0] => a [1] => b [2] => c [3] => d )
Array ( [0] => d [1] => c [2] => b [3] => a) The
sort() and rsort() functions sort the array from low to high, and the return result is a bool value;
asort() and arsort() functions preserve the sorting of key values, and the key values ​​are not re-indexed after sorting.
Example 2: Disturbing the order of the array - shuffle() function:

$array = array("a","b","c","d");
shuffle($array);//Sort from low to high
print_r($array);
?>

The result is a dynamic result:
Array ( [0] => c [1] => a [2] => d [3] => b )
The result of shuffle is a bit random, and it is different every time it is refreshed.
Example 3: array_reverse() array reverse:

$array = array("d","b","a","c");
$array = array_reverse($array);//Sort from low to high
print_r($array);
?>

Run result:
Array ( [0] => c [1] => a [2] => b [3] => d )
Example 4: Natural sorting algorithm - natsort() and natcasesort();

$array = array("sort2","Sort5","sort1","sort4");
natsort($array);//Sort from low to high
print_r($array);
echo "
";
natcasesort($array);
print_r($array);
?>

Result:
Array ([1] => Sort5 [2] => sort1 [0] => sort2 [3] => sort4 )
Array ( [2] => sort1 [0] => sort2 [3] => sort4 [1] => Sort5 )
natsort() and natcasesort() perform natural sorting on arrays, which is the normal sorting algorithm using numbers. natcasesort ignores case.
Example 5: Sort the array by key value ksort():

$array = array(1=>"sort2",4=>"Sort5",2=>"sort1",3=>"sort4");
ksort($array);//Sort from low to high
print_r($array);
?>

Result:
Array ([1] => sort2 [2] => sort1 [3] => sort4 [4] => Sort5 )
Note: The ksort() function re-indexes.
8. Other uses of arrays

cout($array) -------- Count the number of cells in the array
　Array_diff($array1,$array2)----------Counts the differences between arrays and returns what is in the first array but not in the second array.
　array_diff_assoc($array1,$array2)---------Same as array_diff(), except that it also compares key values
　array_diff_key($array1,$array2)------------Compare key values
　array_product($array)----------Returns the product of all numbers in the array
　array_sum($array)--------------The sum of all values
　array_rand($array,$n)----------take out $n values ​​​​from the $array array and return the array
　array_intersect($array1,$array2)----------------Get the intersection of two arrays
　array_intersect_assoc($array1,$array2)---------------in array_intersect Perform key-value comparison on the basis of
　array_intersect_key($array1,$array2)-----------------Compare the intersection of two array key values ​​

The above introduces the skills and operation summary of PHP arrays, including the relevant content. I hope it will be helpful to friends who are interested in PHP tutorials.