Home>Article>Backend Development> How to make an array retain only key names in php
Two implementation methods: 1. Use the array_keys() function to obtain all key names of the array, with the syntax "array_keys (array)"; if you want to retain the key names of the specified value, you can set the second and third Parameters, syntax "array_keys (array, specified value, type is consistent)". 2. Use a foreach loop and an empty array to obtain all the key names of the array. The syntax is "foreach($arr1 as $k=>$v){$arr2[]=$k;}".
The operating environment of this tutorial: windows7 system, PHP version 8.1, DELL G3 computer
php Two ways to make the array only retain key names
Method 1: Use the array_keys() function to get all the key names of the array
array_keys() The function can retrieve some or all keys in the array.
array_keys(array,value,strict)
| Parameters | Description |
|---|---|
| array | Required . Specifies an array. |
| value | Optional. You can specify a key value, and then only the key name corresponding to that key value will be returned. |
| strict | Optional. Used with the value parameter. Possible values:
|
When you want to get all key names, just set the first parameter and omit the second and third parameters.
Example:
"Peter","Age"=>"41","Country"=>"USA"); var_dump($arr); $keys=array_keys($arr); echo "数组只保留键名:"; var_dump($keys); ?>
If you want to get the key name of the specified value, the second and third parameters are not omitted
"Peter","Age1"=>"41","Age2"=>41,"Country"=>"USA"); var_dump($arr); $keys1=array_keys($arr,41); echo "数组只保留键名:"; var_dump($keys1); $keys2=array_keys($arr,41,true); var_dump($keys2); ?>
Method 2: Use a foreach loop and an empty array to get all the key names of the array
Implementation idea:
Use a foreach loop to traverse the key names and key values of the original array, and only assign the key names to the empty array.
Example:
11,"bbb"=>22,"ccc"=>33); var_dump($arr1); $arr2=array(); foreach($arr1 as $k=>$v){ $arr2[]=$k; } echo "数组只保留键名:"; var_dump($arr2); ?>
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