Analysis of precautions for modifying array key with array_unshift() in PHP, array_unshiftkey_PHP tutorial

Analysis of precautions for modifying array key by array_unshift() in php, array_unshiftkey

This article analyzes the precautions for modifying array key by array_unshift() in php. Share it with everyone for your reference, the details are as follows:

As we all know, array_unshift() is used to add elements to the beginning of the array, but today I suddenly discovered that if the key value of the array is of numeric type (or can be converted to numeric type), array_unshift() will modify all keys The Key of a numeric element is really a trap

Example:

$a=array(111=>"dddddddddddd","112"=>array("one"=>"orange","two"=>"hhhhh"), "113"=>array("one"=>"orange","two"=>"hhhhh"),"oooo"=>"jjjjj");
print_r($a);echo "</br>";
array_unshift($a, "aaaaaaaaa");
print_r($a);echo "</br>";

Output result:

Array ( [111] => dddddddddddd [112] => Array ( [one] => orange [two] => hhhhh ) [113] => Array ( [one] => orange [two] => hhhhh ) [oooo] => jjjjj )
Array ( [0] => aaaaaaaaa [1] => dddddddddddd [2] => Array ( [one] => orange [two] => hhhhh ) [3] => Array ( [one] => orange [two] => hhhhh ) [oooo] => jjjjj )

You see, the array key value has changed after array_unshift(), the original 111 has become 1, what a trap! Everyone needs to pay special attention to this when using array_unshift() in the future!

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I hope this article will be helpful to everyone in PHP programming.