Get an alternative to a specified column value in an array
This article aims to provide an alternative to obtaining the specified column value of an array in PHP, and solve the problem of repeated definition of the array_column() function. For old versions of PHP and new versions of PHP, corresponding solutions are given respectively, and code examples are provided to help developers better process array data.
In PHP development, the array_column() function is a very practical tool, which can easily extract the values of a specified column from a multi-dimensional array and form a new array. However, in some cases, developers may encounter an error with "Cannot redeclare array_column()", which is usually because the function is repeatedly defined in the code. This article will provide two solutions to this problem.
Solution 1: Polyfill implementation compatible with old versions of PHP
If your project needs to be compatible with older PHP versions (below PHP 5.5) and these versions themselves do not support the array_column() function, then you may need to implement an array_column() polyfill yourself. To avoid conflicts with PHP's built-in array_column() function, you should check whether the function already exists before defining it.
The following is an example implementation of the array_column() function that is compatible with old versions of PHP:
if (!function_exists('array_column')) {
/**
* Return the value of a single column from a multidimensional array*
* @param array $array Enter the array* @param mixed $column_key Column to return the value* @param mixed $index_key as column for the index/key of the return array* @return array
*/
function array_column(array $array, $column_key, $index_key = null): array
{
$result = [];
foreach ($array as $sub_array) {
if (!is_array($sub_array)) {
continue;
}
if (is_null($index_key) && array_key_exists($column_key, $sub_array)) {
$result[] = $sub_array[$column_key];
} elseif (array_key_exists($index_key, $sub_array) && array_key_exists($column_key, $sub_array)) {
$result[$sub_array[$index_key]] = $sub_array[$column_key];
}
}
return $result;
}
}
Notes:
- function_exists('array_column') is used to check if the function already exists and ensures that the definition is not repeated.
- The polyfill implements the basic functions of the array_column() function, including extracting the value of the specified column and optional index columns.
- Use type declaration: array requires PHP 7.
Solution 2: Delete custom functions
If your project has been upgraded to a newer PHP version (PHP 5.5 and above) and no longer needs to be compatible with older versions, the easiest solution is to directly delete your customized array_column() function. Because the new version of PHP has built-in this function, it does not need to be implemented by itself.
Summarize:
When resolving the "Cannot redeclare array_column()" error, you must first determine whether your project needs to be compatible with older versions of PHP. If compatibility is required, use polyfill with function_exists() check; if compatibility is not required, directly delete the custom array_column() function and use the built-in functions in PHP. Choosing the right solution can effectively solve the problem and improve the maintainability of the code.
The above is the detailed content of Get an alternative to a specified column value in an array. For more information, please follow other related articles on the PHP Chinese website!
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