preg_filter
Description
The preg_filter of PCRE for PHP perform a regular expression search and replace.
preg_filter() is identical to preg_replace() except it only returns the (possibly transformed) subjects where there was a match.
Syntax
preg_filter(
string|array $pattern,
string|array $replacement,
string|array $subject,
int $limit = -1,
int &$count = null
): string|array|nullParameters
pattern
The pattern to search for. It can be either a string or an array with strings.
Several PCRE modifiers are also available.
replacement
The string or an array with strings to replace. If this parameter is a string and the pattern parameter is an array, all patterns will be replaced by that string. If both pattern and replacement parameters are arrays, each pattern will be replaced by the replacement counterpart. If there are fewer elements in the replacement array than in the pattern array, any extra patterns will be replaced by an empty string.
replacement may contain references of the form \n or $n, with the latter form being the preferred one. Every such reference will be replaced by the text captured by the n'th parenthesized pattern. n can be from 0 to 99, and \0 or $0 refers to the text matched by the whole pattern. Opening parentheses are counted from left to right (starting from 1) to obtain the number of the capturing subpattern. Note that backslashes in string literals may require to be escaped.
When working with a replacement pattern where a backreference is immediately followed by another number (i.e.: placing a literal number immediately after a matched pattern), you cannot use the familiar \1 notation for your backreference. \11, for example, would confuse preg_replace() since it does not know whether you want the \1 backreference followed by a literal 1, or the \11 backreference followed by nothing. In this case the solution is to use ${1}1. This creates an isolated $1 backreference, leaving the 1 as a literal.
When using the deprecated e modifier, this function escapes some characters (namely ', ", \ and NULL) in the strings that replace the backreferences. This is done to ensure that no syntax errors arise from backreference usage with either single or double quotes (e.g. 'strlen('$1')+strlen("$2")'). Make sure you are aware of PHP's string syntax to know exactly how the interpreted string will look.
subject
The string or an array with strings to search and replace.
If subject is an array, then the search and replace is performed on every entry of subject, and the return value is an array as well.
limit
The maximum possible replacements for each pattern in each subject string. Defaults to -1 (no limit).
count
If specified, this variable will be filled with the number of replacements done.
Return
Returns an array if the subject parameter is an array, or a string otherwise.
If no matches are found or an error occurred, an empty array is returned when subject is an array or null otherwise.
Examples
1 · pattern replacement subject · string
<? $pattern = '#dog#'; $replacement = 'alpaca'; $subject = 'The brown-and-white dog jumps over the other brown-and-white dog.'; $return = preg_filter($pattern, $replacement, $subject); echo $return;
The brown-and-white alpaca jumps over the other brown-and-white alpaca.
2 · pattern replacement subject · array
<?
$pattern =
[
'#dog#',
'#brown#',
'#white#'
];
$replacement =
[
'alpaca',
'black',
'gray'
];
$subject =
[
'The brown-and-white dog jumps over the other brown-and-white dog.',
'The brown-and-white dog jumps over',
'the other brown-and-white dog.'
];
$return = preg_filter($pattern, $replacement, $subject);
print_r($return);
Array
(
[0] => The black-and-gray alpaca jumps over the other black-and-gray alpaca.
[1] => The black-and-gray alpaca jumps over
[2] => the other black-and-gray alpaca.
)
3 · limit
<?
$pattern =
[
'#dog#',
'#brown#',
'#white#'
];
$replacement =
[
'alpaca',
'black',
'gray'
];
$subject =
[
'The brown-and-white dog jumps over the other brown-and-white dog.',
'The brown-and-white dog jumps over',
'the other brown-and-white dog.'
];
$limit = 1;
$return = preg_filter($pattern, $replacement, $subject, $limit);
print_r($return);
Array
(
[0] => The black-and-gray alpaca jumps over the other brown-and-white dog.
[1] => The black-and-gray alpaca jumps over
[2] => the other black-and-gray alpaca.
)
4 · count
<?
$pattern =
[
'#dog#',
'#brown#',
'#white#'
];
$replacement =
[
'alpaca',
'black',
'gray'
];
$subject =
[
'The brown-and-white dog jumps over the other brown-and-white dog.',
'The brown-and-white dog jumps over',
'the other brown-and-white dog.'
];
$limit = 1;
$return = preg_filter($pattern, $replacement, $subject, $limit, $count);
print_r($return);
echo $count;
ACDComment
5 · digit
<?
$pattern =
[
'#\d#'
];
$replacement =
[
'✓'
];
$subject =
[
'abcdefghijklmnopqrstuvwxyz',
'ABCDEFGHIJKLMNOPQRSTUVWXYZ',
'1234567890',
'!@#$%^&*()',
'`-=[]\;,./',
'~_+\{}|:"<>?',
'match a digit 1776'
];
$return = preg_filter($pattern, $replacement, $subject);
print_r($return);
11: ACDComment 254: NewSubFile 255: SubFile 256: ImageWidth 257: ImageLength 258: BitsPerSample 259: Compression 262: PhotometricInterpretation 266: FillOrder 269: DocumentName 270: ImageDescription 271: Make 272: Model 273: StripOffsets 274: Orientation 277: SamplesPerPixel 278: RowsPerStrip 279: StripByteCounts 280: MinSampleValue 281: MaxSampleValue 282: XResolution 283: YResolution 284: PlanarConfiguration 285: PageName 286: XPosition 287: YPosition 288: FreeOffsets 289: FreeByteCounts 290: GrayResponseUnit 291: GrayResponseCurve 292: T4Options 293: T6Options 296: ResolutionUnit 297: PageNumber 301: TransferFunction 305: Software 306: DateTime 315: Artist 316: HostComputer 317: Predictor 318: WhitePoint 319: PrimaryChromaticities 320: ColorMap 321: HalfToneHints 322: TileWidth 323: TileLength 324: TileOffsets 325: TileByteCounts 330: SubIFD 332: InkSet 333: InkNames 334: NumberOfInks 336: DotRange 337: TargetPrinter 338: ExtraSample 339: SampleFormat 340: SMinSampleValue 341: SMaxSampleValue 342: TransferRange 343: ClipPath 344: XClipPathUnits 345: YClipPathUnits 346: Indexed 347: JPEGTables 351: OPIProxy 512: JPEGProc 513: JPEGInterchangeFormat 514: JPEGInterchangeFormatLength 515: JPEGRestartInterval 517: JPEGLosslessPredictors 518: JPEGPointTransforms 519: JPEGQTables 520: JPEGDCTables 521: JPEGACTables 529: YCbCrCoefficients 530: YCbCrSubSampling 531: YCbCrPositioning 532: ReferenceBlackWhite 700: ExtensibleMetadataPlatform 769: Gamma 770: ICCProfileDescriptor 771: SRGBRenderingIntent 800: ImageTitle
6 · non-digit
<?
$pattern =
[
'#\D#',
];
$replacement =
[
'✓',
];
$subject =
[
'abcdefghijklmnopqrstuvwxyz',
'ABCDEFGHIJKLMNOPQRSTUVWXYZ',
'1234567890',
'!@#$%^&*()',
'`-=[]\;,./',
'~_+\{}|:"<>?',
'match a digit 1776'
];
$return = preg_filter($pattern, $replacement, $subject);
print_r($return);
Array
(
[0] => ✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓
[1] => ✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓
[3] => ✓✓✓✓✓✓✓✓✓✓
[4] => ✓✓✓✓✓✓✓✓✓✓
[5] => ✓✓✓✓✓✓✓✓✓✓✓✓
[6] => ✓✓✓✓✓✓✓✓✓✓✓✓✓✓1776
)
7 · word
<?
$pattern =
[
'#\w#'
];
$replacement =
[
'✓'
];
$subject =
[
'abcdefghijklmnopqrstuvwxyz',
'ABCDEFGHIJKLMNOPQRSTUVWXYZ',
'1234567890',
'!@#$%^&*()',
'`-=[]\;,./',
'~_+\{}|:"<>?',
'match a word_'
];
$return = preg_filter($pattern, $replacement, $subject);
print_r($return);
Array
(
[0] => ✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓
[1] => ✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓✓
[2] => ✓✓✓✓✓✓✓✓✓✓
[5] => ~✓+\{}|:"<>?
[6] => ✓✓✓✓✓ ✓ ✓✓✓✓✓
)
8 · non-word
<?
$pattern =
[
'#\W#'
];
$replacement =
[
'✓'
];
$subject =
[
'abcdefghijklmnopqrstuvwxyz',
'ABCDEFGHIJKLMNOPQRSTUVWXYZ',
'1234567890',
'!@#$%^&*()',
'`-=[]\;,./',
'~_+\{}|:"<>?',
'match a word_'
];
$return = preg_filter($pattern, $replacement, $subject);
print_r($return);
Array
(
[3] => ✓✓✓✓✓✓✓✓✓✓
[4] => ✓✓✓✓✓✓✓✓✓✓
[5] => ✓_✓✓✓✓✓✓✓✓✓✓
[6] => match✓a✓word_
)
9 · ?
<? $pattern = '#\w?#'; $replacement = '✓'; $subject = '0 or 1 time'; $return = preg_filter($pattern, $replacement, $subject); echo $return;
✓✓ ✓✓✓ ✓✓ ✓✓✓✓✓
10 · *
<? $pattern = '#\w*#'; $replacement = '✓'; $subject = '0 or more times'; $return = preg_filter($pattern, $replacement, $subject); echo $return;
✓✓ ✓✓ ✓✓ ✓✓
11 · +
<? $pattern = '#\w+#'; $replacement = '✓'; $subject = '1 or more times'; $return = preg_filter($pattern, $replacement, $subject); echo $return;
✓ ✓ ✓ ✓
12 · whitespace
<? $pattern = '#\s\s+#'; $replacement = ' '; $subject = ' too many spaces'; $return = preg_filter($pattern, $replacement, $subject); echo $return;
too many spaces
13 · non-whitespace
<? $pattern = '#\S\S+#'; $replacement = '✓'; $subject = ' too many spaces'; $return = preg_filter($pattern, $replacement, $subject); echo $return;
✓ ✓ ✓
14 · group
<? $pattern = '#(\w+) (\d+), (\d+)#i'; $replacement = '$1 1, $3'; $subject = 'January 31, 2001'; $return = preg_filter($pattern, $replacement, $subject); echo $return;
January 1, 2001
15 · several
<?
$pattern =
[
'#(19|20)(\d{2})-(\d{1,2})-(\d{1,2})#',
'#^\s*{(\w+)}\s*=#'
];
$replacement =
[
'\3/\4/\1\2',
'$\1 ='
];
$subject = '{startDate} = 1999-9-29';
$return = preg_filter($pattern, $replacement, $subject);
echo $return;
$startDate = 9/29/1999
16 · compare preg_replace
<?
$pattern =
[
'#\d#',
'#[a-z]#',
'#[1a]#'
];
$replacement =
[
'A:$0',
'B:$0',
'C:$0'
];
$subject =
[
'1',
'a',
'2',
'b',
'3',
'A',
'B',
'4'
];
$return1 = preg_replace($pattern, $replacement, $subject);
$return2 = preg_filter($pattern, $replacement, $subject);
print_r($return1);
print_r($return2);
1776283233 = 2026-04-15 20:00:33
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