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When using PHP for multibyte string processing, mb_eregi_replace is a very practical function that supports regular replacement of multibyte encoding and is case-insensitive. However, many developers encounter a confusion when using it: the replacement result looks like an array, but it is actually a string.
This article will analyze this phenomenon to help you correctly understand the return value type and usage of mb_eregi_replace .
mb_eregi_replace is a multi-byte regular replacement function provided by the PHP mbstring extension. Its function is similar to preg_replace , but it is optimized for the multi-byte character set. Its function prototype is as follows:
<code> string mb_eregi_replace ( string $pattern , string $replacement , string $string [, string $option = "msr" ] ) </code>Parameter description:
$pattern : Regular expression pattern, case-insensitive.
$replacement : The replaced string.
$string : The target string to be searched for.
$option : Regular expression modifier, defaults to "msr" .
The return value is the replaced string.
In many cases, developers will find calls:
<code> $result = mb_eregi_replace('pattern', 'replacement', $subject); var_dump($result); </code>An array-like structure will appear in the output result, for example:
<code> string(14) "Array(content)" </code>This is actually because the replacement string $replacement contains variables or the $subject itself has an array-like string form, or the regular capture group reference is used in the $replacement , but the reference content is not processed correctly, resulting in the replaced string appearing to contain array information.
Another common misunderstanding is that regular capture groups (such as \\1 , $1 ) are understood as arrays, but in fact they are only manifested as text in strings.
Suppose you have the following string:
<code> $subject = "Welcome to m66.net, which is a test string."; </code>I want to use mb_eregi_replace to replace the domain name as example.com , and the writing method is as follows:
<code> $result = mb_eregi_replace('m66\.net', 'example.com', $subject); echo $result; </code>Output:
<code> Welcome to example.com, which is a test string. </code>What is returned here is the string type, and $result is not an array.
The array type is used in the replacement string:
If $replacement is passed into an array, not a string, an error will be caused, but this will usually report an error and will not silently return a string that looks like an array.
Misunderstanding the capture group used in the replacement content:
Suppose you use:
<code> $result = mb_eregi_replace('(m66\.net)', '$1.com', $subject); </code>Here $1 is a capture group reference, but if it is not parsed correctly, it may cause the replaced string to become the literal $1.com , making people mistakenly think it is an array or a special structure.
mb_eregi_replace return value is always a string .
If you see the result "like array", check if the replacement string and the input string contain content that may cause confusion.
When using capture groups correctly, make sure the syntax is correct and avoid outputting unexpected content.
Using var_dump during debugging can help confirm variable types.
$result = mb_eregi_replace($pattern, $replacement, $subject);
echo $result; // Output: Please visit example.com for more information.
?>
</code>
