PHP find first of occurrence of string

As long as FirstName:, LastName: and City: will always be in there, you should be able to just get the positions of all three and see which one occurs first with min().

$string = "United States City: Chicago FirstName: Mike LastName: Doe";
$firstname = strpos($string, 'FirstName:');
$lastname = strpos($string, 'LastName:');
$city = strpos($string, 'City:');

$position = min($firstname, $lastname, $city);
switch($position){
   case $firstname:
      $first_parameter = 'FirstName:';
      break;
   case $lastname:
      $first_parameter = 'LastName:';
      break;
   case $city:
      $first_parameter = 'City:';
      break;
}

You'll have your first parameter and the position.

I think the cleanest and most straightforward way to do this (though a sexy regex is tempting) is to put your parameters in an array and foreach through it.

$params = array(
    'FirstName:',
    'LastName:',
    'City:',
);

$first = null; # First parameter
$first_pos = null; # First parameter position

foreach($params as $var)
{
    $pos = strpos($string, $var);
    if($pos < $first_pos || null === $first_pos)
    {
        $first = $var;
        $first_pos = $pos;
    }
}

If you change your params, just change the array.

First, strip off the "United States ": $str2 = substr($string, 0, strlen("United States "))

Then find the field: preg_match('/^([^:]+): /', $str2)

The position of the first parameter should be constant: strlen("United States ")

$string = "United States FirstName: Mike LastName: Doe City: Chicago";
$i = strpos($string, ":");           // Find the first colon
while ($string[$i] != " ") { $i--; } // work backwards until we hit a space
// First parameter's name now starts at $i + 1