Regular
Expressions
101
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Explanation
/
^
[
+-
]
?
(?!
\.
(?!
\d
)
|
$
)
\d
*
(?:
\.
\d
*
)?(?:
(?<=
[
\d
.
]
)
e
[
+-
]
?
\d
+
)?
$
/
igm
^
asserts position at start of a line
Match a single character present in the list below
[
+-
]
?
matches the previous token between
zero
and
one
times, as many times as possible, giving back as needed
(greedy)
+-
matches a single character in the list
+-
(case insensitive)
Negative Lookahead
(?!
\.
(?!
\d
)
|
$
)
Assert that the Regex below does not match
1st Alternative
\.
(?!
\d
)
\.
matches the character
.
with index
46
10
(
2E
16
or
56
8
) literally (case insensitive)
Negative Lookahead
(?!
\d
)
Assert that the Regex below does not match
\d
matches a digit (equivalent to
[0-9]
)
2nd Alternative
$
$
asserts position at the end of a line
\d
matches a digit (equivalent to
[0-9]
)
*
matches the previous token between
zero
and
unlimited
times, as many times as possible, giving back as needed
(greedy)
Non-capturing group
(?:
\.
\d
*
)?
?
matches the previous token between
zero
and
one
times, as many times as possible, giving back as needed
(greedy)
\.
matches the character
.
with index
46
10
(
2E
16
or
56
8
) literally (case insensitive)
\d
matches a digit (equivalent to
[0-9]
)
*
matches the previous token between
zero
and
unlimited
times, as many times as possible, giving back as needed
(greedy)
Non-capturing group
(?:
(?<=
[
\d
.
]
)
e
[
+-
]
?
\d
+
)?
?
matches the previous token between
zero
and
one
times, as many times as possible, giving back as needed
(greedy)
Positive Lookbehind
(?<=
[
\d
.
]
)
Assert that the Regex below matches
Match a single character present in the list below
[
\d
.
]
\d
matches a digit (equivalent to
[0-9]
)
.
matches the character
.
with index
46
10
(
2E
16
or
56
8
) literally (case insensitive)
e
matches the character
e
with index
101
10
(
65
16
or
145
8
) literally (case insensitive)
Match a single character present in the list below
[
+-
]
?
matches the previous token between
zero
and
one
times, as many times as possible, giving back as needed
(greedy)
+-
matches a single character in the list
+-
(case insensitive)
\d
matches a digit (equivalent to
[0-9]
)
+
matches the previous token between
one
and
unlimited
times, as many times as possible, giving back as needed
(greedy)
$
asserts position at the end of a line
Global pattern flags
i modifier:
i
nsensitive. Case insensitive match (ignores case of
[a-zA-Z]
)
g modifier:
g
lobal. All matches (don't return after first match)
m modifier:
m
ulti line. Causes
^
and
$
to match the begin/end of each line (not only begin/end of string)
Match Information
Your regular expression does not match the subject string.
Try launching the debugger to find out why.
Quick Reference
Regular Expression
v3
No Match
/
/
igm
Test String
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Generated Code
Loading code sample...
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report.
For a full regex reference for PHP, please visit:
http://php.net/manual/en/ref.pcre.php
Regular
Expressions
101
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