Loop through each character in a string in PHP

The other day I was working on a project that required me to extract a numeric ID from the current page’s URL. The problem was that the ID could either be at the end of the URL string or in the middle, depending if there were any parameters added on or not. Here is how I worked around the problem by looping through each character of the string.

Because the first part of the URL was formatted normally I could use a combination of strpos() and substr() to find the part of the string that contained the ID as well as all the characters that followed it (I could have used regex here, but I prefer to avoid using it if I can help it). This still left me with the problem of getting the ID out of that string, as the actual number could be any length. Luckily for me, the ID was immediately followed by a non-numeric character, so I came up with a solution where I could loop through each character in the string and use each one for the required ID, but stop the loop when I hit the first character that was not a number. In the interest of sharing some useful code, here is the simple snippet that I used to loop through the string along with my use case:

View this gist on GitHub

23 responses to “Loop through each character in a string in PHP”

Joel Day

July 9, 2012 at 10:39 pm

Rather than using substr you could just use $str[$i] which should be a little faster 🙂

Reply
1. Hugh Lashbrooke
  
  July 10, 2012 at 2:43 pm
  
  Thanks for the input, but I don’t think that would work because $str isn’t an array (unless there’s something I’m missing).
  
  Reply
  1. naresh
    
    August 22, 2012 at 3:28 am
    
    strings are treated/considered as array of char elements 🙂
    
    Reply
    1. Hugh Lashbrooke
      
      August 22, 2012 at 2:43 pm
      
      Yeah – after posting that above comment and actually learned exactly that. It’s a handy thing to know for the future!
      
      Reply
    2. Andrea
      
      November 6, 2014 at 4:14 am
      
      You can use $str{$i} which worked for me in looking at a specific character is a string.
      
      Example:
      Code:
      $string = ‘0123’;
      for ($i=0; $i < strlen($string); $i++)
      {
      echo $i."=".$string{$i}."”;
      }
      Result:
      0=0
      1=1
      2=2
      3=3
      
      Reply
  2. TheMyth
    
    December 21, 2017 at 11:30 am
    
    I want to simply validate a name where there should be no numbers,
    eg: Harr8y = false
    Im new and not very good at PHP, what would be the best way to go through each character
    as ctype_digit does not work because it checks the whole string
    
    Reply
2. christian
  
  January 30, 2015 at 9:37 am
  
  not recommended bro.
  
  you might get ‘Uninitialized string offset’ for the unexpected user input.
  
  Thanks.
  
  Reply
3. christian
  
  January 30, 2015 at 9:43 am
  
  andrea
  
  try running your code again,
  you miss the 0 value. hehehehe
  
  Reply
NIikhil Zachariah

September 26, 2013 at 11:25 am

Thank You So much

Reply
NIikhil Zachariah

September 26, 2013 at 11:26 am

thank U!!!!!!!!!!!!!!!

Reply
TempleClause

October 17, 2013 at 9:25 pm

I think rather than using
for( $i = 0; $i <= $strlen; $i++ ) {
you should use < $strlen

But thanks for the rest 😀

Reply
Sumit Gupta

November 6, 2014 at 12:43 pm

Though it is too late, but PHP has inbuilt function of str_split that can be used to iterate after converting string to array. One of example there has function that works for Unicode character, as default str_split of above mention method won’t work there.

Reply
christian

January 30, 2015 at 9:29 am

Joel Day, naresh
try testing

if(char[0] == ‘ ‘)….

if the char contains 0 values it return as a null value.

Hugh Lashbrooke saves the day. wehehehe
though its already been a year. Thank you bro.

Reply
christian

January 30, 2015 at 9:33 am

i mean
what if the input is
$input = 0123;
for($i = 0;$i <=strlen($input );$i++ ){
echo $input[$i]; //when it goes to the first array value it would detect null value. program noticed. not good.
}
Thanks again.

Reply
1. Christian
  
  August 21, 2017 at 8:01 pm
  
  You can not iterate through a number the same way you can iterate through a string. If you turn $input into a string first then you can use echo $input[$i].
  
  Reply
christian

January 30, 2015 at 9:35 am

i mean
$input = ‘0123’;//wehehehe

Reply
D’angelo Williams

March 25, 2015 at 3:00 am

Thank you, this was exactly what I needed. You da best

Reply
Ali

June 21, 2015 at 12:25 pm

Here is my solution to the problem you had Hugh,
I tried to obvious method to me atleast.
is there difference in how you it and mine in terms of performance?

//return id from a string
function GetID($str)
{

$length=strlen($str);
$id=””;
for ($i=0; $i < $length; $i++)
{
if(is_numeric($str[$i]))
{
$id=$id.$str[$i];
}
else
{
break;
}
}
return $id;
}
echo " The ID is = ".GetID("1235?valu");

Reply
ram

July 6, 2015 at 6:11 am

$str = “String to loop through”;

Reply
Joachim Coyoca

July 18, 2015 at 4:31 am

what if i had a table visitor contains a field of id, name, year and department and another table of department which contains a field of id, year and department_name…. the department value would be BSHRM AND BSCRiM and etc.. in every entry of visitor, how could i convert every department into an integer??? for example… first loop would be BSHRM will be equal to 1, and second loop BSHRM equal to 2, until all BSHRM will finish to convert into number….. someone there.. please help me… heres my email..for those who are willing to help.. [email protected]…. thank you 🙂

Reply
Sajjad

March 16, 2016 at 8:17 pm

$str = “123456789”
$len = strlen( $str );
for( $i = 0; $i <= $len; $i++ ) {
$a.=$i;
}
// Output
/*
0
1
2
3
4
5
6
7
8
9
*/
😀

Reply
Chris Nasr

October 7, 2016 at 4:46 pm

You should really be using mb_strlen, not strlen, unless your intention is to traverse the string as if it were raw data.

Reply
Shashidhar. A. R

October 21, 2016 at 3:26 am

Hello sir…
I have one doubt.
Define stringwalk?

Reply