Check for PHP Syntax errors?

Question

Well, I have run into a bit of a pickle here. I am needing to check some PHP for syntax errors. I noticed this bit that needs to run from the commandline:

php -l somefile.php

However, is there a way to run this from within a PHP file itself? I've been looking and have think that I can use parse_str function somehow to accomplish this by entering it into a $_GET, but can't quite understand how this works.

Someone else told me to use token_get_all() php function to determine this.

But I can't figure out how to do this with any approach? Can anyone here give me some sample code to get started perhaps?? I don't think using eval() is the way to go, although I had an eval($code) working, but don't think I should run the script if there are PHP syntax errors.

Any help on this is greatly appreciated, as always!

@SolomonClosson, I think he's terse comment is referring to php.net/manual/en/function.exec.php — Pacerier
– Pacerier, Commented Jan 28, 2015 at 7:59

Mike Brant · Accepted Answer · 2012-08-14 21:10:36Z

6

You could simply do shell_exec() like this:

$output = shell_exec('php -l /path/to/filename.php');

This gives you the output of the command line operation in the string $output.

answered Aug 14, 2012 at 21:10

Mike Brant

71.4k10 gold badges102 silver badges104 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Solomon Closson Over a year ago

Ok, have fixed the undefined output error, however, now it returns an empty string regardless if there are PHP Syntax errors or not.

Wolfgang Blessen Over a year ago

Using exec() instead of shell_exec() will give you the output in the third parameter: php.net/manual/en/function.exec.php

Rudie · Accepted Answer · 2018-08-07 19:16:39Z

5

I use token_get_all for this. I have some PHP code in the db. Before saving, I do

function is_valid_php_code_or_throw( $code ) {
        $old = ini_set('display_errors', 1);
        try {
                token_get_all("<?php\n$code", TOKEN_PARSE);
        }
        catch ( Throwable $ex ) {
                $error = $ex->getMessage();
                $line = $ex->getLine() - 1;
                throw new InvalidInputException("PARSE ERROR on line $line:\n\n$error");
        }
        finally {
                ini_set('display_errors', $old);
        }
}

Works like a charm. Syntax only. No missing variables, type incompayibility etc.

InvalidInputException is my own. You can make it anything, or return a bool, or handle the exception yourself.

I'm not sure if display_errors is necessary. It was at some point.

answered Aug 7, 2018 at 19:16

Rudie

54.2k42 gold badges137 silver badges176 bronze badges

2 Comments

Sean Morris Over a year ago

This string parses but crashes if your try to run it <?php class {CLASS}: 3v4l.org/p9k1Y

Rudie Over a year ago

Eh. That's weird. But you should add the TOKEN_PARSE flag: 3v4l.org/VFDrG

Mandy Schoep · Accepted Answer · 2017-05-29 07:25:46Z

4

It is safer to check the return status of php -l

$fileName = '/path/to/file.php';
exec("php -l {$fileName}", $output, $return);

if ($return === 0) {
    // Correct syntax
} else {
    // Syntax errors
}

See this fiddle to see it in action

answered May 29, 2017 at 7:25

Mandy Schoep

98111 silver badges19 bronze badges

Comments

P.O.W. · Accepted Answer · 2024-08-30 09:18:56Z

1

From command line use -ln to return the line containing the error.

> php -ln file.php

Parse error: syntax error, unexpected ':' in file.php on line 899
Errors parsing file.php

answered Aug 30, 2024 at 9:18

P.O.W.

2,3051 gold badge18 silver badges17 bronze badges

1 Comment

mwfearnley May 1 at 12:07

-l does a syntax check ("lint"), -n prevents it from using php.ini. I suppose php.ini often contains display_errors=off. To overcome this directly, you can do php -ddisplay_errors=on, but perhaps it's not generally desirable to bother reading php.ini when only a syntax check is desired.

Samuil Banti · Accepted Answer · 2015-12-14 10:12:33Z

0

I would do it like this:

$php_file = 'The path to your file';
if(substr(`php -l $php_file`, 0, 16) == 'No syntax errors') {
    // Correct syntax
} else {
    // Error
}

answered Dec 14, 2015 at 10:12

Samuil Banti

1,8351 gold badge16 silver badges31 bronze badges

Comments

wanovak · Accepted Answer · 2012-08-14 21:08:15Z

-1

php_check_syntax should do the trick. If you're running PHP >= 5.05, see the first comment in the comments section for the implementation.

edited Aug 14, 2012 at 21:08

answered Aug 14, 2012 at 21:03

wanovak

6,12727 silver badges32 bronze badges

3 Comments

Solomon Closson Over a year ago

This function was removed from PHP... link

wanovak Over a year ago

Good catch @SolomonClosson. OP, luckily in the comments is an implementation that you can use. I won't paste it here as it's very large, but it's the top comment.

mario Over a year ago

This is a PHP4 function and has been removed in PHP 5.0.x. Moreover it was basically just an alias to eval() - it just ran the supplied code to detect parsing errors.

Community · Accepted Answer · 2017-05-23 11:53:28Z

-1

You can use exec to check for syntax errors.

$tempFile = path/of/file
$syntaxParseError = strpos(exec('php -l '.$tempFile), 'No syntax errors detected') === false;`

Unfortunately, this will not give you the line number or tell you anything about the error. For that you will either need to install static analyzer on your server Is there a static code analyzer [like Lint] for PHP files? or write your own parser.

NB. token_get_all() will not determine anything on its own, but it useful function for making a parser.

edited May 23, 2017 at 11:53

CommunityBot

11 silver badge

answered Feb 10, 2017 at 2:47

Dan Bray

7,9024 gold badges61 silver badges72 bronze badges

Comments

kjdion84 · Accepted Answer · 2017-07-17 06:41:39Z

-2

Why use the shell at all?

function syntax_is_valid($code)
{
    try
    {
        @eval($code);
    }
    catch (ParseError $e)
    {
        return false;
    }

    return true;    
}

Alternatively use $e->getMessage() for more info.

edited Jul 17, 2017 at 6:41

answered Jul 17, 2017 at 5:14

kjdion84

10.1k8 gold badges64 silver badges91 bronze badges

1 Comment

CJ Dennis Over a year ago

How do you prevent all the side effects from running (evaling) the code? Such as printing, connecting to the database, writing files, etc.

Collectives™ on Stack Overflow

Check for PHP Syntax errors?

8 Answers 8

2 Comments

2 Comments

Comments

1 Comment

Comments

3 Comments

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

8 Answers 8

2 Comments

2 Comments

Comments

1 Comment

Comments

3 Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related