README

s9e\RegexpBuilder is a single-purpose library that generates a regular expression that matches a given list of strings.

Simply put, given ['foo', 'bar', 'baz'] as input, the library will generate /(?:ba[rz]|foo)/.

Usage

$builder = new s9e\RegexpBuilder\Builder;
echo '/', $builder->build(['foo', 'bar', 'baz']), '/';

/(?:ba[rz]|foo)/

Examples

UTF-8 input with UTF-8 output

$builder = new s9e\RegexpBuilder\Builder([
	'input'  => 'Utf8',
	'output' => 'Utf8'
]);
echo '/', $builder->build(['☺', '☹']), '/u';

/[☹☺]/u

Raw input with raw output

Note that the output is shown here MIME-encoded as it is not possible to display raw bytes in UTF-8. Raw output is most suitable when the result is saved in binary form, e.g. in a data cache.

$builder = new s9e\RegexpBuilder\Builder([
	'input'  => 'Bytes',
	'output' => 'Bytes'
]);
echo '/', quoted_printable_encode($builder->build(['☺', '☹'])), '/';

/=E2=98[=B9=BA]/

Raw input with PHP output

For PHP regular expressions that do not use the u flag. PHP output is most suitable for regexps that are used into PHP sources, in conjunction with var_export(). The output itself is ASCII, with non-ASCII and non-printable characters escaped.

$builder = new s9e\RegexpBuilder\Builder([
	'input'  => 'Bytes',
	'output' => 'PHP'
]);
echo '/', $builder->build(['☺', '☹']), '/';

/\xE2\x98[\xB9\xBA]/

UTF-8 input with PHP output

For PHP regular expressions that use the u flag.

$builder = new s9e\RegexpBuilder\Builder([
	'input'  => 'Utf8',
	'output' => 'PHP'
]);
echo '/', $builder->build(['☺', '☹']), '/u';

/[\x{2639}\x{263A}]/u

UTF-8 input with JavaScript output

For JavaScript regular expressions that do not use the u flag and need the higher codepoints to be split into surrogates. The regexp itself uses only ASCII characters, with non-ASCII and non-printable characters escaped.

$builder = new s9e\RegexpBuilder\Builder([
	'input'        => 'Utf8',
	'inputOptions' => ['useSurrogates' => true],
	'output'       => 'JavaScript'
]);
echo '/', $builder->build(['☺', '☹']), "/\n";
echo '/', $builder->build(['😁', '😂']), '/';

/[\u2639\u263A]/
/\uD83D[\uDE01\uDE02]/

UTF-8 input with Unicode-aware JavaScript output

For JavaScript regular expressions that use the u flag introduced in ECMAScript 6. In that case, you can simply forgo using surrogates.

$builder = new s9e\RegexpBuilder\Builder([
	'input'  => 'Utf8',
	'output' => 'JavaScript'
]);
echo '/', $builder->build(['☺', '☹']), "/u\n";
echo '/', $builder->build(['😁', '😂']), '/u';

/[\u2639\u263A]/u
/[\u{1F601}\u{1F602}]/u

Custom delimiters

$strings = ['/', '(', ')', '#'];

$builder = new s9e\RegexpBuilder\Builder;
echo '/', $builder->build($strings), "/\n";

$builder = new s9e\RegexpBuilder\Builder(['delimiter' => '#']);
echo '#', $builder->build($strings), "#\n";

$builder = new s9e\RegexpBuilder\Builder(['delimiter' => '()']);
echo '(', $builder->build($strings), ')';

/[#()\/]/
#[\#()/]#
([#\(\)/])

Lowercase hexadecimal representation

By default, the PHP and JavaScript output uses uppercase hexadecimal symbols, e.g. \xAB. This can be changed to lowercase using the outputOptions setting.

$builder = new s9e\RegexpBuilder\Builder([
	'input'         => 'Bytes',
	'output'        => 'PHP',
	'outputOptions' => ['case' => 'lower']
]);
echo '/', $builder->build(['☺', '☹']), "/\n";

$builder = new s9e\RegexpBuilder\Builder([
	'input'         => 'Utf8',
	'output'        => 'JavaScript',
	'outputOptions' => ['case' => 'lower']
]);
echo '/', $builder->build(['☺', '☹']), '/';

/\xe2\x98[\xb9\xba]/
/[\u2639\u263a]/

Using meta-characters

Some individual characters can be used to represent arbitrary expressions in the input strings. The requirements are that:

1. Only single characters (as per the input encoding) can be used. For example, ? is allowed but not ??.
2. The regular expression must be valid on its own. For example, .* is valid but not +.

In the following example, we emulate Bash-style jokers by mapping ? to . and * to .*.

$builder = new s9e\RegexpBuilder\Builder([
	'meta' => ['?' => '.', '*' => '.*']
]);
echo '/', $builder->build(['foo?', 'bar*']), '/';

/(?:bar.*|foo.)/

In the following example, we map X to \d. Note that sequences produced by meta-characters may appear in character classes if the result is valid.

$builder = new s9e\RegexpBuilder\Builder([
	'meta' => ['X' => '\\d']
]);
echo '/', $builder->build(['a', 'b', 'X']), '/';

/[\dab]/