Introduction to commonly used array functions in PHP_PHP tutorial

Introduction to commonly used array functions in PHP

How can you program without arrays? The following are the array processing functions commonly used when learning PHP. One principle to follow in programming is the DRY (Don`t Repeat Yourself) principle. There are a large number of functions in PHP. It is not practical to remember these functions, but commonly used functions still need to be used skillfully. The use of most functions Methods can be used by consulting the PHP manual.

It is indispensable to consult manuals in programming, so you must learn to use existing things. For example, the array processing function in PHP already has a sorting function. Why bother to write something that is fake? Soak or stack or quick queue.

Programming is an indirect process and a process of reuse. To write good code, design patterns are indispensable for support. It may be difficult for beginners to learn design patterns (just like when I first looked at design patterns, It’s a bit laborious), but when you have accumulated a certain amount of code, when you study design patterns, you feel that design patterns are really useful and can help you write beautiful code. Having said that, I got a little off track, so let’s summarize the commonly used functions for array operations in PHP.

Some readers may feel that the commonly used functions for arrays summarized below are a bit lacking. Will the flames be high if everyone adds firewood? If you feel that there are other commonly used array processing functions, please leave a comment. Don’t be stingy with your knowledge. , isn’t it a very happy thing to share things with others? Also, the code below is from my own hand, but it was written two years ago. Everyone is welcome to criticize and correct me.

　array_splice() deletes the specified element in the array

Array_splice (array name, number of items to delete from front to back, new size of an array); without the third parameter, there is no returned array. When there is no third parameter, the meaning of the second parameter is from front to back. Keep a few

exp:

　$my_array=array( //Create an array

　"hehe"=>"haha",

　"A"=>"lu",

　"lu"=>"ge"

　);

　$new=array_splice($my_array,1,3); //Use array_splice (array name, number of items to delete from front to back, new size of an array);

var_dump($new);

　?>

Result: array(2) { ["A"]=> string(2) "lu" ["lu"]=> string(2) "ge" }

2. Traversal of foreach() array

Usage: foreach (array as key name => key value) or foreach (array as key value)

exp:

　$my_array=array( //Create an array

　"hehe"=>"haha",

　"A"=>"lu",

　"lu"=>"ge"

　);

foreach($my_array as $key=>$value)

　{

echo $key."=>".$value."
";

　}

　?>

Output result:

hehe=>haha

　A=>lu

lu=>ge

3. Sorting of arrays

　(1)sort() and rsort() sort by key value sort() from small to large, rsort() from large to small

sort () exp :

　$my_array=array(1,2,3,6,7,8,9,4,5);//Create an array

sort($my_array);

foreach($my_array as $keys=>$value)

　{

echo $keys."=>".$value."
";

　}

　?>

Output result:

　0=>1

　1=>2

　2=>3

　3=>4

　4=>5

　5=>6

　6=>7

　7=>8

　8=>9

rsort() exp:

　$my_array=array(1,2,3,6,7,8,9,4,5);//Create an array

rsort($my_array);

foreach($my_array as $keys=>$value)

　{

echo $keys."=>".$value."
";

　}

　?>

Output result:

　0=>9

　1=>8

　2=>7

　3=>6

　4=>5

　5=>4

　6=>3

　7=>2

　8=>1

(2).asort() and arsort() have the same principle as above, but do not change the corresponding relationship between key names and key values ​​

exp:

　$my_array=array(1,2,3,6,7,8,9,4,5);//Create an array

asort($my_array);

foreach($my_array as $keys=>$value)

　{

echo $keys."=>".$value."
";

　}

　?>

Output result:

　0=>1

　1=>2

　2=>3

　7=>4

　8=>5

　3=>6

　4=>7

　5=>8

　6=>9

(3)ksort() and krsort() are sorting by key name

　4. Mathematical functions of arrays

　array_sum() calculates the sum of all key values ​​in the array count() calculates the number of elements

exp:

　$my_array=array(1,2,3,6,7,8,9,4,5);//Create an array

echo array_sum($my_array);

　?>

Output result: 45

5. Other functions

　array_unique() removes the same elements in the array

in_array() checks whether a value is in the array (returns true and false)

Array_search() returns the key or value, and returns the key name corresponding to the key value

shuffle() disrupts the original array

　$my_array=array(1,2,3,6,7,8,9,4,5,5,5,5);//Create an array

　array_unique($my_array);//Remove the same elements in the array

var_dump($my_array);

echo "
";

echo in_array(5,$my_array);

echo "
";

　$new=array_search(6,$my_array);//Returns the key name corresponding to the key value

echo $new;

　?>

Output result:

　array(12) { [0]=> int(1) [1]=> int(2) [2]=> int(3) [3]=> int(6) [4 ]=> int(7) [5]=> int(8) [6]=> int(9) [7]=> int(4) [8]=> int(5) [9 ]=> int(5) [10]=> int(5) [11]=> int(5) }

　1

　3

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