php - Why won't preg_match work?

Answer

Solution:

Your regex pattern need delimiters:

function validate($email){
  $regex = "/...your pattern.../";
  if (preg_match($regex, $email)) { 
      return true;
  } else {
      return false;
  }
}
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EDIT: AND then you need to escape the delimiters characters in your regex, if present.

Using / as delimiter, you got two in your pattern:

$regex = "/^((([a-z]|[0-9]|!|#|$|%|&|'|\*|\+|\-|\/|=|\?|\^|_|`|\{|\||\}|~)+(\.([a-z]|[0-9]|!|#|$|%|&|'|\*|\+|\-|\/|=|\?|\^|_|`|\{|\||\}|~)+)*)@((((([a-z]|[0-9])([a-z]|[0-9]|\-){0,61}([a-z]|[0-9])\.))*([a-z]|[0-9])([a-z]|[0-9]|\-){0,61}([a-z]|[0-9])\.(af|ax|al|dz|as|ad|ao|ai|aq|ag|ar|am|aw|au|at|az|bs|bh|bd|bb|by|be|bz|bj|bm|bt|bo|ba|bw|bv|br|io|bn|bg|bf|bi|kh|cm|ca|cv|ky|cf|td|cl|cn|cx|cc|co|km|cg|cd|ck|cr|ci|hr|cu|cy|cz|dk|dj|dm|do|ec|eg|sv|gq|er|ee|et|fk|fo|fj|fi|fr|gf|pf|tf|ga|gm|ge|de|gh|gi|gr|gl|gd|gp|gu|gt| gg|gn|gw|gy|ht|hm|va|hn|hk|hu|is|in|id|ir|iq|ie|im|il|it|jm|jp|je|jo|kz|ke|ki|kp|kr|kw|kg|la|lv|lb|ls|lr|ly|li|lt|lu|mo|mk|mg|mw|my|mv|ml|mt|mh|mq|mr|mu|yt|mx|fm|md|mc|mn|ms|ma|mz|mm|na|nr|np|nl|an|nc|nz|ni|ne|ng|nu|nf|mp|no|om|pk|pw|ps|pa|pg|py|pe|ph|pn|pl|pt|pr|qa|re|ro|ru|rw|sh|kn|lc|pm|vc|ws|sm|st|sa|sn|cs|sc|sl|sg|sk|si|sb|so|za|gs|es|lk|sd|sr|sj|sz|se|ch|sy|tw|tj|tz|th|tl|tg|tk|to|tt|tn|tr|tm|tc|tv|ug|ua|ae|gb|us|um|uy|uz|vu|ve|vn|vg|vi|wf|eh|ye|zm|zw|com|edu|gov|int|mil|net|org|biz|info|name|pro|aero|coop|museum|arpa))|(((([0-9]){1,3}\.){3}([0-9]){1,3}))|(\[((([0-9]){1,3}\.){3}([0-9]){1,3})\])))$/";
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EDIT 2:

about the error you were getting

Warning: preg_match() [function.preg-match]: No ending delimiter '^' found ...
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it found the^ character as first character in your pattern, taking it as a delimiter, and complained because it did not find a matching^ delimiter ending the pattern.

Answer

Solution:

You can do this withoutpreg_xx altogether:

function validate($email)
{
    return filter_var($email, FILTER_VALIDATE_EMAIL);
}

if (false === validate($email)) {
    // invalid email given
}
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It uses together with