Analysis of Extracting Substring from PHP String

2021-12-12 08:06:19
OfStack

In this paper, an example is given to describe the operation of extracting substrings from PHP strings. Share it for your reference, as follows:

Problem

You want to extract part 1 of a string from a specific position in the string. For example, for a user name entered into a 1 form, you want to get the first 8 characters of that user name.

Solve

Use substr() Select substring


$substring = substr($string,$start,$length);
$username = substr($_GET['username'],0,8);

Discuss

1. If both $strart and $length are positive numbers, substr() Returns a string of $lenfth characters starting with $start. The first position of the character is 0.


echo substr('I Love PHP!',3,5);

ove P

If you ignore $length, substr() Returns a substring from $strart to the end of the original string.

Positive starting position, no length specified


echo substr('I Love PHP!',3);

ove PHP!

If $start is greater than the length of the string, substr() false will be returned

If $start plus $length exceeds the end of the string, substr() Returns all characters from $start to the end of the string


echo substr('I Love PHP!',3,9);

ove PHP!

If $start is negative, substr() The reciprocal from the end of the string determines where the substring begins


echo substr('I Love PHP!',-4);

PHP!


echo substr('I Love PHP!',-4 , 3);

PHP

If the value of $start is negative and exceeds the beginning of the string, substr() Will treat $start as 0

If $length is negative, substr() It will count down from the end of the string to determine where it ends


echo substr('I Love PHP!',3 , -1);

Love PHP


echo substr('I Love PHP!',-4 , -2);

PH