This Is What Causes The Fatal Error: [] Operator Not Supported For Strings In PHP 7.1 And How To Fix It
As a WordPress developer, you may have encountered the dreaded "Fatal error: [] operator not supported for strings" error, particularly if you're working with PHP 7.1 or later. This error can be frustrating, but understanding the underlying cause and how to resolve it is crucial for maintaining a robust and bug-free codebase.
In this article, we'll dive into the root of this issue, explore real-world examples, and provide step-by-step guidance on how to effectively fix the "[] operator not supported for strings" error in your PHP 7.1 (or later) WordPress projects.
Understanding the "[] Operator Not Supported for Strings" Error
The "[] operator not supported for strings" error occurs when you attempt to use the array access operator ([]
) on a variable that is not an array, but rather a string. This change in behavior was introduced in PHP 7.1, as part of the language's ongoing efforts to improve type safety and consistency.
Prior to PHP 7.1, accessing a string as if it were an array (e.g., $string[0]
) would return the character at the specified index. However, this was considered a "magic" behavior that could lead to unexpected results and potential security vulnerabilities. As a result, the PHP development team decided to make this behavior more explicit, requiring developers to use dedicated string functions (such as substr()
) instead of the array access operator.
Here's an example of the error in action:
$w_custom_font1_src = 'Arial';
echo $w_custom_font1_src[0]; // Fatal error: [] operator not supported for strings
In this case, the code attempts to access the first character of the $w_custom_font1_src
string using the array access operator, which is no longer allowed in PHP 7.1 and later.
Real-World Scenario: A WordPress Plugin Example
Let's consider a more realistic scenario where this error might occur in a WordPress plugin or theme.
Imagine you have a WordPress plugin that allows users to customize the font used on their website. The plugin might have a settings page where users can enter the font name and source. Your plugin code might look something like this:
// Get the custom font settings from the database
$w_custom_font1_name = get_option('w_custom_font1_name', 'Arial');
$w_custom_font1_src = get_option('w_custom_font1_src', 'https://fonts.googleapis.com/css?family=Arial');
// Use the custom font settings in the <head> section of the website
add_action('wp_head', function() use ($w_custom_font1_name, $w_custom_font1_src) {
echo "<style>
body {
font-family: '{$w_custom_font1_name}', sans-serif;
}
</style>";
echo "<link rel='stylesheet' href='{$w_custom_font1_src}' />";
});
In this example, the plugin retrieves the custom font settings from the WordPress options table and then uses them to generate the necessary HTML and CSS to apply the custom font to the website.
However, if the user enters a font name (e.g., "Arial") instead of a complete font URL (e.g., "https://fonts.googleapis.com/css?family=Arial") as the font source, the $w_custom_font1_src
variable will be a string, not an array. When the plugin tries to use the $w_custom_font1_src
variable in the <link>
tag, it will trigger the "[] operator not supported for strings" error.
How to Diagnose and Fix the "[] Operator Not Supported for Strings" Error
Now that you understand the root cause of the "[] operator not supported for strings" error, let's walk through the steps to diagnose and fix the issue in your WordPress project.
-
Identify the Problematic Code: Start by locating the specific code that's causing the error. In the example above, the error would occur in the wp_head
action callback, where the plugin is attempting to use the $w_custom_font1_src
variable in the <link>
tag.
-
Determine the Variable Type: Verify the type of the variable that's triggering the error. In this case, it's likely that the $w_custom_font1_src
variable is a string, not an array.
-
Reinitialize the Variable as an Array: If the variable is supposed to be an array, you'll need to reinitialize it as an array. In the WordPress plugin example, you can do this by modifying the code that retrieves the custom font settings from the database:
// Get the custom font settings from the database
$w_custom_font1_name = get_option('w_custom_font1_name', 'Arial');
$w_custom_font1_src = get_option('w_custom_font1_src', array('https://fonts.googleapis.com/css?family=Arial'));
In this updated code, we've set the default value of $w_custom_font1_src
to an array containing the default font source URL. This ensures that the variable is always an array, even if the user has not yet set a custom font source.
-
Use Appropriate String Functions: If the variable is supposed to be a string, you'll need to use the appropriate string functions instead of the array access operator. In the WordPress plugin example, you can update the wp_head
action callback to use the substr()
function instead of the array access operator:
add_action('wp_head', function() use ($w_custom_font1_name, $w_custom_font1_src) {
echo "<style>
body {
font-family: '{$w_custom_font1_name}', sans-serif;
}
</style>";
echo "<link rel='stylesheet' href='{$w_custom_font1_src}' />";
});
Alternatively, you can use the strpos()
function to check if the variable is a string, and then use the appropriate string manipulation functions:
add_action('wp_head', function() use ($w_custom_font1_name, $w_custom_font1_src) {
echo "<style>
body {
font-family: '{$w_custom_font1_name}', sans-serif;
}
</style>";
if (is_string($w_custom_font1_src) && strpos($w_custom_font1_src, 'http') === 0) {
echo "<link rel='stylesheet' href='{$w_custom_font1_src}' />";
} else {
echo "<link rel='stylesheet' href='https://fonts.googleapis.com/css?family={$w_custom_font1_src}' />";
}
});
In this updated code, we first check if $w_custom_font1_src
is a string, and then use the strpos()
function to determine if it starts with "http" (indicating a full URL). If so, we use the string as-is in the <link>
tag. If not, we assume it's a font name and construct the full font URL manually.
By following these steps, you can effectively diagnose and fix the "[] operator not supported for strings" error in your WordPress projects, ensuring that your code remains robust and compatible with the latest version of PHP.
Remember, the key to resolving this issue is to properly manage the types of your variables and use the appropriate string or array functions, depending on the expected data format. By taking the time to understand and address this error, you'll be well on your way to writing more reliable and maintainable WordPress code.
If you're looking for a powerful tool to help you identify and fix technical issues like this one, as well as optimize your website's conversion rates, be sure to check out Flowpoint.ai. Flowpoint uses AI-powered analytics to detect and recommend solutions for a wide range of technical, UX, and content-related problems that can impact your website's performance
Get a Free AI Website Audit
Automatically identify UX and content issues affecting your conversion rates with Flowpoint's comprehensive AI-driven website audit.