PHP doesn't use the given variable

Question

My HTML form:

<form action="lambda.php" method="post">
<label><input type="number" name="intfield" id="intfield"/></label>
<input type="submit" value="Go!"/>
</form>

Part of PHP code:

$hello = intval($_POST["intfield"]);

$client = LambdaClient::factory(array(
            'version' => "latest",
            'credentials' => array(
                'key' => 'blurred',
                'secret' => 'blurred'
            ),
            'region' => 'us-west-2'
        ));

$response = $client->invoke([
    'FunctionName' => 'helloworld2',
    'InvocationType' => 'RequestResponse',
    'Payload' => '{"key1":"$hello"}',
        ]);

echo($response['Payload']->__toString());
echo $hello;

Basically I want to type a number into the form of the HTML which is then given to the PHP code. The PHP file should send the number to a function in Lambda (Amazon Web Services).

My Lambda function and the PHP is fine. It works fine if I hardcode the number in the PHP like that:

'Payload' => '{"key1":"7"}',

But obviously I want to use it with a variable. The last echo in the PHP code shows the proper number though. Can you find a mistake in my PHP code? Thanks!

and i think '{"key1":"$hello"}' print as a string not with value. — devpro
– devpro, Commented Oct 27, 2016 at 15:53
try like that: 'Payload' => json_encode(array('key1'=>$hello)), — devpro
– devpro, Commented Oct 27, 2016 at 15:54

devpro · Accepted Answer · 2016-10-27 16:21:26Z

The variable $hello treated as a string in your code because of string quotes:

You can test like:

$hello = intval(1); // initialize a variable.

Than make an array:

$response = [
'FunctionName' => 'helloworld2',
'InvocationType' => 'RequestResponse',
'Payload' => '{"key1":"$hello"}',
];

print_r($response);

Result:

Array
(
    [FunctionName] => helloworld2
    [InvocationType] => RequestResponse
    [Payload] => {"key1":"$hello"}
)

Above mentioned result tell you each and everything whats wrong in your code now when i fixed the quotes issue and using json_encode() for your desired output:

<?php
$hello = intval(1);
$response = [
'FunctionName' => 'helloworld2',
'InvocationType' => 'RequestResponse',
'Payload' => json_encode(array('key1'=>$hello)),
];
echo "<pre>";
print_r($response);
?>

It gives me correct result:

Array
(
    [FunctionName] => helloworld2
    [InvocationType] => RequestResponse
    [Payload] => {"key1":1}
)

Sylwester · Accepted Answer · 2016-10-27 16:01:15Z

0

Single quote strings in PHP does not expand variables. Thus you are passing the string '$hello' and not the value of $hello to the service. By changing is to "{\"key1\":\"{$hello}\"}" it will pass the value of the variable.

Always use single quotes to make constant strings. Use double quotes if you need escapes like "\n" or expansion like "test: {$test}".

Always validate your strings passed by a client so you don't make security issues.

answered Oct 27, 2016 at 16:01

Sylwester

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