PHP Regular Expressions Reading Records with a Pattern Separator - Web Development and Design | Tutorial for Java, PHP, HTML, Javascript PHP Regular Expressions Reading Records with a Pattern Separator - Web Development and Design | Tutorial for Java, PHP, HTML, Javascript

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Tuesday, July 9, 2019

PHP Regular Expressions Reading Records with a Pattern Separator

PHP Regular Expressions


Reading Records with a Pattern Separator

Problem

You want to read in records from a file, in which each record is separated by a pattern you can match with a regular expression.

Solution

Read the entire file into a string and then split on the regular expression:

       $contents = file_get_contents('/path/to/your/file.txt');
       $records = preg_split('/[0-9]+\) /', $contents);

Discussion

This breaks apart a numbered list and places the individual list items into array elements. So if you have a list like this:

       1) Gödel
       2) Escher
       3) Bach

you end up with a four-element array, with an empty opening element. That’s because preg_split() assumes the delimiters are between items, but in this case, the numbers are before items:

       array(4) {
            [0]=>
            string(0) ""
            [1]=>
            string(7) "Gödel
       "
            [2]=>
            string(7) "Escher
       "
            [3]=>
            string(5) "Bach
       "
       }

From one point of view, this can be a feature, not a bug, because the nth element holds the nth item. But, to compact the array, you can eliminate the first element:

       $records = preg_split('/[0-9]+\) /', $contents);
       array_shift($records);

Another modification you might want is to strip newlines from the elements and substitute the empty string instead:

       $records = preg_split('/[0-9]+\) /', str_replace("\n",'',$contents));
       array_shift($records);

PHP doesn’t allow you to change the input record separator to anything other than a newline, so this technique is also useful for breaking apart records divided by strings. However, if you find yourself splitting on a string instead of a regular expression, substitute explode() for preg_split() for a more efficient operation.

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