How do I remove a comma off the end of a string?

I want to remove the comma off the end of a string. As it is now I am using

$string = substr($string,0,-1);

but that only removes the last character of the string. I am adding the string dynamically, so sometimes there is no comma at the end of the string. How can I have PHP remove the comma off the end of the string if there is one at the end of it?

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最佳答案 
$string = rtrim($string, ',');

Docs for rtrim here

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Precede that with:

if(substr($string, -1)==",")
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if(substr($str, -1, 1) == ',') {


$str = substr($str, 0, -1);


}

http://php.net/manual/en/function.substr.php

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have a look at the rtrim function 

rtrim ($string , ",");

the above line will remove a char if the last char is a comma

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A simple regular expression would work

$string = preg_replace("/,$/", "", $string)
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rtrim ($string , ","); is the easiest way.

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i guess you're concatenating something in the loop, like

foreach($a as $b)
$string .= $b . ',';

much better is to collect items in an array and then join it with a delimiter you need

foreach($a as $b)
$result[] = $b;


$result = implode(',', $result);

this solves trailing and double delimiter problems that usually occur with concatenation

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This is a classic question, with two solutions. If you want to remove exactly one comma, which may or may not be there, use:

if (substr($string, -1, 1) == ',')
{
$string = substr($string, 0, -1);
}

If you want to remove all commas from the end of a line use the simpler:

$string = rtrim($string, ',');

The rtrim function (and corresponding ltrim for left trim) is very useful as you can specify a range of characters to remove, i.e. to remove commas and trailing whitespace you would write:

$string = rtrim($string, ", \t\n");
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I had a pesky "invisible" space at the end of my string and had to do this

 $update_sql=rtrim(trim($update_sql),',');

But a solution above is better

 $update_sql=rtrim($update_sql,', ');
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If you're concatenating something in the loop, you can do it in this way too:

$coma = "";
foreach($a as $b){
$string .= $coma.$b;
$coma = ",";
}

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