Regex - get string after full date and before standard text - regex

Question

I'm stuck on another regex. I'm extracting email data. In the below example, only the time, date and message in quotes changes.
Message Received 6:06pm 21st February "Hello. My name is John Smith" Some standard text.
Message Received 8:08pm 22nd February "Hello. My name is "John Smith"" Some standard text.
How can I get the message only if I need to start with the positive lookbehind, (?<=Message Received ) to begin searching at this particular point of the data? The message will always start and end with quotes but the user is able to insert their own quotes as in the second example.

Answer 1

You can just use a negated charcter class in a capturing group:
/Message Received.*?"([^\n]+)"/
Snippet:
$input = 'Message Received 6:06pm 21st February "Hello. My name is John Smith" Some standard text.
Message Received 8:08pm 22nd February "Hello. My name is "John Smith"" Some standard text.}';
preg_match_all('/Message Received.*?"([^\n]+)"/', $input, $matches);
foreach ($matches[1] as $match) {
echo $match . "\r\n";
}
Output:
> Hello. My name is John Smith
> Hello. My name is "John Smith"

Answer 2

For extracting message in between double quotes.
(?=Message Received)[^\"]+\K\"[\w\s\"\.]+\"
Regex demo

Answer 3

You capture the message in a group
(?<=Message Received)[^"]*(.*)(?=\s+Some standard text)

Answer 4

Two out of the other three posted answers on this page provide an incorrect result. None of the other posted answers are as efficient as they could be:
To correctly extract the substring between the outer double quotes, use one of the following patterns:
/Message Received[^"]+"\K[^\n]+(?=")/ (No capture group, takes 132 steps, Demo)
/Message Received[^"]+"([^\n]+)"/ (Capture group, takes 130 steps, Demo)
Both patterns provide maximum accuracy and efficiency using negated character classes leading up to and including the targeted substring. The first pattern reduces preg_match_all()'s output array bloat by 50% by using \K instead of a capture group. For these reasons, one of these patterns should be used in your project. As your input string increases in size, my patterns provide increasingly better performance versus the other posted patterns.
PHP Implementation:
$in represents your input string.
Pattern #1 Method:
var_export(preg_match_all('/Message Received[^"]+"\K[^\n]+(?=")/',$in,$out)?$out[0]:[]);
// notice the output array only has elements in the fullstring subarray [0]
Output:
array (
0 => 'Hello. My name is John Smith',
1 => 'Hello. My name is "John Smith"',
)
Pattern #2 Method:
var_export(preg_match_all('/Message Received[^"]+"([^\n]+)"/',$in,$out)?$out[1]:[]);
// notice because a capture group is used, [0] subarray is ignored, [1] is used
Output:
array (
0 => 'Hello. My name is John Smith',
1 => 'Hello. My name is "John Smith"',
)
Both methods provide the desired output.
Anirudha's incorrect pattern: /(?<=Message Received)[^"]*(.*)(?=\s+Some standard text)/ (345 steps + a capture group + includes the unwanted outer double quotes)
Josh Crozier's pattern: /Message Received.*?"([^\n]+)"/ (174 steps + a capture group)
Sahil Gulati's incorrect pattern: /(?=Message Received)[^\"]+\K\"[\w\s\"\.]+\"/ (109 steps + includes the unwanted outer double quotes + unnecessarily escapes characters in the pattern)