3 methods: 1. Use substr(), set the second parameter to 0 and the third parameter to N. The syntax is "substr(string,0,N)". 2. Use mb_substr(), set the second parameter to 0, and set the third parameter to N. The syntax is "mb_substr (string, 0, N, character encoding)". 3. Use substr_replace(), set the second parameter to 0, and set the third parameter to N. The syntax is "substr_replace(string,'',N)".
The operating environment of this tutorial: windows7 system, PHP version 8.1, DELL G3 computer
php wants to intercept the string from 0 to N-digit characters can be realized by 3 functions:
Use substr() function
Use mb_substr() function
Use the substr_replace() function
Method 1: Use the substr() function to intercept the string
## The #substr() function can intercept characters of a certain length from a specified position in a string.
substr(string,start,length)
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Parameters
Description
string
Required . Specifies a part of the string to be returned.
start
Required. Specifies where in the string to begin.
Positive number - starts at the specified position in the string Negative number - starts at the specified position from the end of the string 0 - at the first character in the string Start at
length
Optional. Specifies the length of the string to be returned. The default is until the end of the string.
Positive number - Returns from the position of the start parameter Negative number - Returns from the end of the string
Just set the second parameter of the function to 0 and the third parameter to N.
Note: The substr() function handles English as There is no problem, but in development we often deal with Chinese characters more. Although the substr() function can also handle Chinese characters, it is not perfect. So how to intercept Chinese characters? You can use the mb_substr() function.
Method 2: Use the mb_substr() function to intercept a string
The mb_substr() function can intercept a specified part of a string, which is different from the substr() function. What's more, the mb_substr() function is not only valid for English characters, but also for Chinese characters.
mb_substr(string,start,length,encoding)
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Parameters
Description
str
Required . Extracts a substring from this string.
start
Required. Specifies where in the string to begin.
Positive number - starts at the specified position in the string Negative number - starts at the specified position from the end of the string 0 - at the first character in the string Start at
length
Optional. Specifies the length of the string to be returned. The default is until the end of the string.
Positive number - Returns from the position of the start parameter Negative number - Returns from the end of the string
encoding
Optional. Character Encoding. If omitted, the internal character encoding is used.
You only need to set the second parameter of the function to 0 and the third parameter to N
Method 3: Use the substr_replace() function to delete the characters after N digits
The substr_replace() function replaces part of the string with another string and returns the replaced character String. You only need to use the substr_replace() function to replace all characters after N digits with null characters, retain the characters from 0 to Nth digit, and return.
substr_replace(string,replacement,start,length)
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Parameters
Description
string
Required . Specifies the string to check.
replacement
Required. Specifies the string to be inserted.
start
Required. Specifies where in the string to begin replacement.
Positive number - starts at the specified position in the string Negative number - starts at the specified position from the end of the string 0 - at the first character in the string Start at
length
Optional. Specifies how many characters to replace. The default is the same as the string length.
Positive number - the length of the string to be replaced Negative number - the number of characters to be replaced from the end of the string 0 - insert instead of replace
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