PHP
Slicing with substr()
Learn to take a portion of a string with substr().
Slicing with substr()
To take only a portion of a string, use substr(). It is called as substr($string, $start, $length); $start is the starting position, $length is the number of characters to take. It returns a new string and does not change the original.
Example: substr('Hello', 0, 3) returns 'Hel'. Positions start at zero, so the first character is at position 0.
Negative start
When $start is negative, PHP counts from the end of the string. substr('Hello', -3) takes the last three characters: 'llo'. This is handy when you want a slice from the end without knowing the length.
Length can also be negative: substr('Hello', 0, -2) gives everything except the last two characters: 'Hel'. Negative values make string handling flexible.
When length is omitted
The $length argument is optional. When it is omitted, substr() takes everything from the starting position to the end of the string. substr('Hello', 3) returns 'lo'.
This is handy for skipping a prefix. For example, to drop the first four characters of a file name, substr($name, 4) is enough. Combined with a negative start, you can make very flexible slices.
Exercise Mask all but the last four digits
Assign "4111-2222-3333-4444" to $card. Use substr() with a negative start to assign the last four digits to $last. Then in a single echo join "****-****-****-" and $last with the . operator.
Show example solution
First assign $card, then $last = substr($card, -4); then add echo "****-****-****-" . $last;
Example solution:
<?php
$card = "4111-2222-3333-4444";
$last = substr($card, -4);
echo "****-****-****-" . $last;
Test yourself
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What does substr('Telephone', 0, 3) return?
substr('Telephone', 0, 3)
Show answer
Tel — Correct. Position 0, length 3 gives 'Tel'.
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Take the last four characters
$code = 'TR2025';
$suffix = substr($code, ____);
echo $suffix;
Show answer
$code = 'TR2025';
$suffix = substr($code, -4);
echo $suffix;
-
What does substr('Hello', -3) return?
substr('Hello', -3)
Show answer
llo — Correct. -3 takes the last three characters: 'llo'.
Next lesson: Searching with strpos()
