Posted in php
578
1:41 am, June 24, 2022
 

using preg_match to extract text from elements

using preg_match to extract specified text from elements

I also tried this search "if you have the start and end of a string extract the middle with php" as thats really all i need it to do, i have the start and the end i just need the middle bit of data. 

i think using strpos and substr this might be easier.

Basically we have to do this:

  1. find the location of the 1st string $html_string

    PHP

    $str_loc = strpos($html_string, "<p><strong>Model</strong>:", 0);


  2. find the location of the next </p> tag after the 1st string. 

    PHP

    $str_loc_end = strpos($html_string, "</p>", $str_loc);


  3. find the length of the 1st string

    PHP

    $start_string = "<p><strong>Model</strong>:";
    $start_string_len = strlen($start_string);
  4. find the length of the 2nd string

    PHP

    $end_string = "</p>";
    $end_string_len = strlen($end_string);


  5. extract the middle bit of text to get what we want
  6. make this into a re-usable function

    Turns out i already had a function that does this here get string between other strings function

PHP

$html_string = "<p><strong>Model</strong>:   Kawasaki ZZR 1400&nbsp; (ZX-14)    </p>";

/* non working example with preg_match */
preg_match('/<p><strong>Model</strong>(.*?)<\/p>/s', $html_string, $match);
echo $match[0];
  
/* testing version with substr and strpos 
use strpos to find the location of the Model and strong and then somehow find the next p tag from that location
*/
 
  /* strpos(string $haystack, string $needle, int $offset = 0): int|false */
  
  
  $str_loc = strpos($html_string, "<p><strong>Model</strong>:", 0);
  echo   "location of the 1st string:".$str_loc; // location of the 1st string.
  echo "<br>";
  
  /* use the offset of the 1st str_loc when looking for the </p> */
  
  $str_loc_end = strpos($html_string, "</p>", $str_loc);
  echo "location of the end of the 1st string container is: ";
  echo  $str_loc_end;
  echo "<br>";
  
  /* string lengths */
  /* we need the strings searched for in variables to count the length for later, this will make functions easier later as well if they are in variables */
  $start_string = "<p><strong>Model</strong>:";
  $end_string = "</p>";
  
  $start_string_len = strlen($start_string);
  $end_string_len = strlen($end_string);
  echo "string lengths: ";
  echo  $start_string_len;
  echo ",";
  echo $end_string_len;
  echo "<br>";

/* using substr we can extract the bits inbetween the start and the end and add it to a variable */
/* substr(string $string, int $offset, ?int $length = null): string */

$start_offset = $str_loc + $start_string_len;
$length_offset = $str_loc_end - $end_string_len;

$final_value = substr($html_string, $start_offset, $length_offset);
echo "the final value is: ";
echo $final_value;

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