There are two main ways to get the last N characters of a string in PHP: 1. Use the substr() function to intercept through the negative starting position, which is suitable for single-byte characters; 2. Use the mb_substr() function to support multilingual and UTF-8 encoding to avoid truncating non-English characters; 3. Optionally determine whether the string length is sufficient to handle boundary situations; 4. It is not recommended to use strrev() substr() combination method because it is not safe and inefficient for multi-byte characters.
To get the last N characters of a string, there are several simple and effective ways to get the last N characters in PHP. The key is to select the appropriate function and pay attention to the boundary situation, such as the processing when the string length is insufficient.
Use substr() function
This is the most common and recommended approach. substr() allows you to intercept substrings of a certain length from the specified position.
$original = "Hello, world!"; $n = 5; $lastN = substr($original, -$n);
- The second parameter uses a negative number to indicate the countdown from the end of the string.
- If the length of the string is less than N, the entire string will be returned directly and there will be no error.
Notes:
- Make sure
$nis a positive integer, otherwise it may lead to unexpected results. - Multi-byte characters (such as Chinese) may cause problems. If you need to support multilinguals, it is recommended to use
mb_substr().
Use mb_substr() to handle multilingual text
If your string may contain non-English characters (such as Chinese under UTF-8 encoding), you should use the multi-byte version of mb_substr() .
$original = "Hello, world!"; $n = 3; $lastN = mb_substr($original, -$n, null, 'UTF-8');
-
nullmeans to be intercepted to the end. -
'UTF-8'specifies character encoding to ensure that each character is correctly recognized.
This can avoid the problem of truncating half a Chinese character or symbol.
Boundary situation processing: What should I do if the string length is insufficient?
Before using it, you can first determine whether the string length is sufficient:
if (mb_strlen($original, 'UTF-8') >= $n) {
$lastN = mb_substr($original, -$n, null, 'UTF-8');
} else {
$lastN = $original;
} Although this is not mandatory (because both substr and mb_substr can be handled automatically), explicit judgments will make the logic clearer, especially when writing complex business logic.
Tips: Use strrev() substr() implement it (not recommended)
Some people will invert the string first, then take the first N characters, and then reverse it back:
$lastN = strrev(substr(strrev($original), 0, $n));
This method:
- Performs for single-byte characters;
- But processing multibyte characters is prone to errors;
- The performance is not as good as using
substr()ormb_substr()directly; - Therefore, it is not recommended to use.
Basically these are the methods. By mastering the differences and usage of substr() and mb_substr() , you can deal with most scenarios.
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