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mb_strcut is part of the mbstring extension in PHP, mainly used for cutting multi-byte character strings. Its functionality is similar to substr, but the difference is that mb_strcut can correctly handle strings with multi-byte characters without causing truncation errors.
mb_strcut(string $str, int $start, int $length = null, string $encoding = null): string
$str: The string to be cut.
$start: The starting position of the cut (in bytes).
$length: The length of the substring (in bytes). If not specified, the substring will extend from $start to the end of the string.
$encoding: The character encoding. The default is the encoding configured in PHP (usually UTF-8).
First, ensure that the string you're using is encoded in UTF-8. Since mb_strcut works with multi-byte characters, the encoding of the string must be correct, and UTF-8 encoding is commonly used.
$str = "Hello, today's weather is great!"; // A string containing Chinese characters and spaces
$encoding = "UTF-8";
If we want to cut the first 6 bytes of the string, we can write:
$sub_str = mb_strcut($str, 0, 6, $encoding);
echo $sub_str; // Output: Hello,
The output will be "Hello,", and it correctly handles the space without causing character truncation.
If you want to cut the string to the end, simply set $length to null:
$sub_str = mb_strcut($str, 0);
echo $sub_str; // Output: Hello, today's weather is great!
A common issue is how to correctly cut strings containing spaces. Spaces can affect the integrity of the string when cutting, especially when using byte-based methods, as spaces can cause inaccurate cutting points.
When using mb_strcut, while it correctly handles multi-byte characters, you still need to keep the following in mind:
Spaces as Characters: In PHP, spaces are considered characters as well. When using mb_strcut to cut a string, spaces are treated as part of the characters. Therefore, you must ensure that the start and length parameters are set correctly.
Ensure Words Are Not Truncated: If you want to cut the string to make sure it's a complete word or phrase, you can use the mb_strrpos function to find the position of the space and then adjust the cutting length based on that position.
Encoding Issues: When calling the mb_strcut function, ensure that the string’s encoding is correct. Mismatched encodings can result in garbled text or incorrect cuts.
Spaces and Special Characters: Since mb_strcut cuts based on byte count, spaces and special characters might be truncated incorrectly. To avoid this, it’s a good idea to check the cut position to ensure it's not in the middle of a character or right before a space.
Performance Considerations: For large-scale string processing, frequent use of mb_strcut can lead to performance issues. It’s recommended to optimize for performance when handling large data and avoid unnecessary string operations.
Suppose we have a string containing multiple words, and we want to cut a part of the string that includes a complete word. We can find the position of the space to ensure the cut is made at a word boundary.
$str = "This is a text containing spaces, let's cut it.";
$encoding = "UTF-8";
<p>// Find the position of the first space<br>
$first_space_pos = mb_strpos($str, ' ', 0, $encoding);</p>
<p>// Cut 10 characters starting from the first space<br>
$sub_str = mb_strcut($str, 0, $first_space_pos + 10, $encoding);<br>
echo $sub_str; // Output: This is a tex<br>
In this example, we avoided truncating a word and instead cut a complete part of the text based on the space position.
