Briefly introduce the troubleshooting method for PHP's exec() function without return value (recommended)

The following editor will bring you a brief discussion of PHP's exec()functionNo return value troubleshooting method (must read). The editor thinks it’s pretty good, so I’ll share it with you now and give it as a reference. Let’s follow the editor and take a look.

In securityimagemagic, exec needs to be used on many serversInstallationfailed

exec() executes externally The command failed without any error message.

exec executes a certain command without any problem on the command line, but an error occurs in php. This problem is 99.99% related to permissions, but the command executed by exec will not return an error. One trick is to use pipe commands, assuming your exec call is as follows:

exec('convert a.jpg b.jpg', $output, $return_val);

can be changed as follows:

exec('convert a.jpg b.jpg 2>&1', $output, $return_val); 


print_r($output);

Use 2>&1, the command will output the error during shell execution to the $output variable, and output the variable for analysis.

Remarks: exec has 3 parameters. The first one is the command to be executed. The second parameter is an array. The value of the array is generated after the first command is executed. , The status of the third parameter execution, 0 indicates success, and the others indicate failure.

There are three functions in php that can be used to execute external commands system, exec, and passthru.

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