Detailed explanation of short array syntax in php5.4

In PHP5.4 and previous versions, we can use square brackets [] to define array elements, as follows:

$array = [1, 2, 3, 4];

This is the so-called "short array syntax" ".

But a more simplified short array syntax was introduced in PHP5.5, using curly braces {} to define array elements, as follows:

$array = ['key1' => 'value1', 'key2' => 'value2'];

This short Array syntax can be more concise and readable in some situations, but it can also cause some problems. For example, if you need to reference an element of an array in a string, using curly braces can cause ambiguity because curly braces are also used for variable substitution in PHP.

If you are using PHP5.4 and previous versions and want to upgrade to PHP5.5 or higher, you need to make changes to the short array syntax in your code. The following are some commonly used modification methods:

1. Replace the square brackets [] with curly brackets {}.

// Before:
$array = [1, 2, 3, 4];

// After:
$array = array(1, 2, 3, 4);

// Before:
$array = ['key1' => 'value1', 'key2' => 'value2'];

// After:
$array = array('key1' => 'value1', 'key2' => 'value2');

2. If both short array syntax and variable substitution appear in your code, you need to use the array() function to explicitly specify the array.

// Before (可能导致歧义)：
echo "The value of the array element is {$array[0]}";

// After：
echo "The value of the array element is " . $array[0];

// 或者：
echo "The value of the array element is {$array[0]}";

// Before (可能导致歧义)：
echo "The value of the array element is {$array['key']}";

// After：
echo "The value of the array element is " . $array['key'];

// 或者：
echo "The value of the array element is {$array['key']}";

3. If your code uses a lot of short array syntax, consider using a tool to automate the replacement operation, such as php-cs-fixer or rephp.

The short array syntax change may cause some tedious work, but it is worth doing. Because in new versions of PHP, the short array syntax has been deprecated and will be removed in a future version. So, updating your code early can make it more robust and sustainable.

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