Checking a String with a Regex in PHP
The capabilities of regular expressions are far from exhausted
by search and replace. There is also the function preg_match,
which checks if a string contains a match
with the regex. The first parameter of the function takes the
regular expression, and the second - the string to
search in.
In this case, if there are many matches, -
the function will find only the first one and finish its
work. Therefore, the function outputs either 1,
or 0 and is used to answer the
question 'is the sought-after present in the string or not'.
Returns one - means yes (and how many times
- is unclear), returns zero - means no.
Let's look at some examples. Let's check,
if the string contains a substring consisting of
the letter 'a', repeated one or more times:
<?php
echo preg_match('#a+#', 'eee aaa bbb'); // outputs 1
?>
And now our string does not contain the sought-after, and the function
will output 0:
<?php
echo preg_match('#a+#', 'eee bbb'); // outputs 0
?>
Determine if the string contains 3 digits
in a row.
Determine if the passed string starts
with http.
Determine if the passed string starts
with http or with https.
Determine if the passed string ends
with the extension txt, html or php.
Determine if the passed string ends
with the extension jpg or jpeg.
