regular express issue with 1 character string

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I am allowing only alpha-numeric, _ & - values in string and removing all other characters. Its working fine but when string size 1 character (does not matter its alphabet or numeric or _ or -), I got empty value instead of single charter.

Here is sample code

$str = 1;
$str = preg_replace('/^[a-zA-Z0-9_-]$/', '', $str);
var_dump($str);

$str = 'a';
$str = preg_replace('/^[a-zA-Z0-9_-]$/', '', $str);
var_dump($str);

I have tested this multiple versions of PHP as well

edited Nov 10 at 12:53

asked Nov 9 at 20:34

Hassaan

4,91541337

1

You might want to remove ^ and $ and use '/[^a-zA-Z0-9_-]/' (a negated character class) if you want to remove those chars you do not want anywhere in a string.
– Wiktor Stribiżew
Nov 9 at 20:35

After removing ^ & $ result is same
– Hassaan
Nov 9 at 20:37

I meant preg_replace('/[^a-zA-Z0-9_-]/', '', $str), => string(1) "a"
– Wiktor Stribiżew
Nov 9 at 20:38

What is expected? You are replacing alpha numerical characters with nothing so an empty string is what I'd expect. Maybe use preg_match instead
– user3783243
Nov 9 at 20:39

1

If that works, you may also use preg_replace('/[^w-]+/', '', $str)
– Wiktor Stribiżew
Nov 9 at 20:41

|
show 6 more comments

up vote
-1
down vote

favorite

Here is sample code

$str = 1;
$str = preg_replace('/^[a-zA-Z0-9_-]$/', '', $str);
var_dump($str);

$str = 'a';
$str = preg_replace('/^[a-zA-Z0-9_-]$/', '', $str);
var_dump($str);

I have tested this multiple versions of PHP as well

edited Nov 10 at 12:53

asked Nov 9 at 20:34

Hassaan

4,91541337

1

You might want to remove ^ and $ and use '/[^a-zA-Z0-9_-]/' (a negated character class) if you want to remove those chars you do not want anywhere in a string.
– Wiktor Stribiżew
Nov 9 at 20:35

After removing ^ & $ result is same
– Hassaan
Nov 9 at 20:37

I meant preg_replace('/[^a-zA-Z0-9_-]/', '', $str), => string(1) "a"
– Wiktor Stribiżew
Nov 9 at 20:38

What is expected? You are replacing alpha numerical characters with nothing so an empty string is what I'd expect. Maybe use preg_match instead
– user3783243
Nov 9 at 20:39

1

If that works, you may also use preg_replace('/[^w-]+/', '', $str)
– Wiktor Stribiżew
Nov 9 at 20:41

|
show 6 more comments

up vote
-1
down vote

favorite

Here is sample code

$str = 1;
$str = preg_replace('/^[a-zA-Z0-9_-]$/', '', $str);
var_dump($str);

$str = 'a';
$str = preg_replace('/^[a-zA-Z0-9_-]$/', '', $str);
var_dump($str);

I have tested this multiple versions of PHP as well

edited Nov 10 at 12:53

asked Nov 9 at 20:34

Hassaan

4,91541337

Here is sample code

$str = 1;
$str = preg_replace('/^[a-zA-Z0-9_-]$/', '', $str);
var_dump($str);

$str = 'a';
$str = preg_replace('/^[a-zA-Z0-9_-]$/', '', $str);
var_dump($str);

I have tested this multiple versions of PHP as well

php regex preg-replace

edited Nov 10 at 12:53

asked Nov 9 at 20:34

Hassaan

4,91541337

edited Nov 10 at 12:53

asked Nov 9 at 20:34

Hassaan

4,91541337

edited Nov 10 at 12:53

asked Nov 9 at 20:34

Hassaan

4,91541337

asked Nov 9 at 20:34

Hassaan

4,91541337

asked Nov 9 at 20:34

Hassaan

4,91541337

1

You might want to remove ^ and $ and use '/[^a-zA-Z0-9_-]/' (a negated character class) if you want to remove those chars you do not want anywhere in a string.
– Wiktor Stribiżew
Nov 9 at 20:35

After removing ^ & $ result is same
– Hassaan
Nov 9 at 20:37

I meant preg_replace('/[^a-zA-Z0-9_-]/', '', $str), => string(1) "a"
– Wiktor Stribiżew
Nov 9 at 20:38

What is expected? You are replacing alpha numerical characters with nothing so an empty string is what I'd expect. Maybe use preg_match instead
– user3783243
Nov 9 at 20:39

1

If that works, you may also use preg_replace('/[^w-]+/', '', $str)
– Wiktor Stribiżew
Nov 9 at 20:41

|
show 6 more comments

1

You might want to remove ^ and $ and use '/[^a-zA-Z0-9_-]/' (a negated character class) if you want to remove those chars you do not want anywhere in a string.
– Wiktor Stribiżew
Nov 9 at 20:35

After removing ^ & $ result is same
– Hassaan
Nov 9 at 20:37

I meant preg_replace('/[^a-zA-Z0-9_-]/', '', $str), => string(1) "a"
– Wiktor Stribiżew
Nov 9 at 20:38

What is expected? You are replacing alpha numerical characters with nothing so an empty string is what I'd expect. Maybe use preg_match instead
– user3783243
Nov 9 at 20:39

1

If that works, you may also use preg_replace('/[^w-]+/', '', $str)
– Wiktor Stribiżew
Nov 9 at 20:41

You might want to remove ^ and $ and use '/[^a-zA-Z0-9_-]/' (a negated character class) if you want to remove those chars you do not want anywhere in a string.
– Wiktor Stribiżew
Nov 9 at 20:35

After removing ^ & $ result is same
– Hassaan
Nov 9 at 20:37

I meant preg_replace('/[^a-zA-Z0-9_-]/', '', $str), => string(1) "a"
– Wiktor Stribiżew
Nov 9 at 20:38

What is expected? You are replacing alpha numerical characters with nothing so an empty string is what I'd expect. Maybe use preg_match instead
– user3783243
Nov 9 at 20:39

If that works, you may also use preg_replace('/[^w-]+/', '', $str)
– Wiktor Stribiżew
Nov 9 at 20:41

|
show 6 more comments

1 Answer
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up vote
1
down vote

accepted

You are removing any chars other than ASCII letters, digits, _ and - anywhere inside the string. You need to remove anchors and convert the positive character class into a negated one:

$str = preg_replace('/[^w-]+/', '', $str);

See the PHP demo online and a regex demo.

Details

[^ - start of a negated character class
- w - a word char: letter, digit or _
- - - a hyphen

] - end of the character class

+ - a quantifier: 1 or more repetitions.

answered Nov 9 at 20:46

Wiktor Stribiżew

301k16122197

add a comment |

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

up vote
1
down vote

accepted

You are removing any chars other than ASCII letters, digits, _ and - anywhere inside the string. You need to remove anchors and convert the positive character class into a negated one:

$str = preg_replace('/[^w-]+/', '', $str);

See the PHP demo online and a regex demo.

Details

[^ - start of a negated character class
- w - a word char: letter, digit or _
- - - a hyphen

] - end of the character class

+ - a quantifier: 1 or more repetitions.

answered Nov 9 at 20:46

Wiktor Stribiżew

301k16122197

add a comment |

up vote
1
down vote

accepted

You are removing any chars other than ASCII letters, digits, _ and - anywhere inside the string. You need to remove anchors and convert the positive character class into a negated one:

$str = preg_replace('/[^w-]+/', '', $str);

See the PHP demo online and a regex demo.

Details

[^ - start of a negated character class
- w - a word char: letter, digit or _
- - - a hyphen

] - end of the character class

+ - a quantifier: 1 or more repetitions.

answered Nov 9 at 20:46

Wiktor Stribiżew

301k16122197

add a comment |

up vote
1
down vote

accepted

You are removing any chars other than ASCII letters, digits, _ and - anywhere inside the string. You need to remove anchors and convert the positive character class into a negated one:

$str = preg_replace('/[^w-]+/', '', $str);

See the PHP demo online and a regex demo.

Details

[^ - start of a negated character class
- w - a word char: letter, digit or _
- - - a hyphen

] - end of the character class

+ - a quantifier: 1 or more repetitions.

answered Nov 9 at 20:46

Wiktor Stribiżew

301k16122197

You are removing any chars other than ASCII letters, digits, _ and - anywhere inside the string. You need to remove anchors and convert the positive character class into a negated one:

$str = preg_replace('/[^w-]+/', '', $str);

See the PHP demo online and a regex demo.

Details

[^ - start of a negated character class
- w - a word char: letter, digit or _
- - - a hyphen

] - end of the character class

+ - a quantifier: 1 or more repetitions.

answered Nov 9 at 20:46

Wiktor Stribiżew

301k16122197

answered Nov 9 at 20:46

Wiktor Stribiżew

301k16122197

answered Nov 9 at 20:46

Wiktor Stribiżew

301k16122197

answered Nov 9 at 20:46

Wiktor Stribiżew

301k16122197

add a comment |

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