Introduction to PHP json_decode
In PHP the inbuilt function json_decode() function is defined as a function as it name suggest it is a function for conversion of any JSON a standard text format objects or decoding of JSON objects to PHP objects, taking a JSON string as a parameter which this function converts or decodes it and returns the encoded values which were in JSON into proper PHP objects. In general, the PHP provides a function that takes a JSON string that usually represents a javascript array or object literals for converting this encoded string in JSON format to a particular PHP object data type.
Working of Json_decode() in PHP
In this article, json_decode() is an inbuilt function provided by PHP for converting or decoding the JSON string into PHP objects where this function takes the JSON data or string which represented as a javascript array as a parameter which is an encoded string is decoded to PHP objects or data types using this json_decode() function and the opposite is done using json_encode() function in PHP.
In the below section we will see syntax and examples of using the json_decode() function:
Syntax:
json_decode(json_string, asso_arr, recur_depth, opt)
Parameters:
Json_string: this parameter is compulsory to specify the JSON encoded string for converting it into PHP objects
- Asso_arr: this parameter is used to specify the Boolean values that can return an associated array if the value is set to true, else returns an object if it is set to false. This parameter is optional and has false as the default value.
- Recur_depth: this parameter is used to specify the depth of the recursion and this is also an optional parameter with 512 as a default value.
- Opt: this parameter is used to specify the bitmask of JSON_OBJECT_AS_ARRAY, JSON_BIGINT_AS_STRING,JSON_INVALID_UTF8_SUBSTITUTE, JSON_THROW_ON_ERROR and this also an optional parameter.
This json_decode() function of PHP takes JSON encoded string as input and returns the value that is decoded to PHP objects which of PHP data types and if the decoding is not possible then this function returns null instead of PHP objects. Now let us see simple example which uses json_decode() of PHP in a HTML structure.
Examples of PHP json_decode
Following are the examples are given below:
Example #1
Code:
<!DOCTYPE html>
<html lang="en">
<head>
<title>Educba- PHP json_decode</title>
</head>
<body>
<?php
$json_string = '{
"CompayName": "Educba",
"Director": "Snehal",
"Employee": "Amardeep",
"address": {
"ColonyName": "Shivaji road",
"city": "Baramati",
"state": "Maharashtra",
"postalCode": "1234567"
},
"TelephoneNumbers": [
{ "type": "Work", "phonenumber": "9876543210" }
]
}';
var_dump(json_decode($json_string, true));
?>
</body>
</html>
Output:
In the above program, we can see when we are writing PHP code in HTML structure we start with “< ?php” then we write the code and at the end the closing tag for PHP code is “? >”. In the above code, we can are declaring a JSON variable as json_string in which we are storing the JSON format data to be converted and then this variable is passed as a parameter to json_decode() function with asso_arr set as “true” that gives it in an array format as shown in the above screenshot. It has array(5) which means it has 5 elements in an array. Suppose we have not set anything or not passed asso_arr parameter such as “var_dump(json_decode($json_string));” then this value would give us access to the property of the object in an array as shown in the below screenshot.
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Now we will see an example below having an invalid JSON format and passing this string to the json_decode() function and what error and output it will give and we will also how to print those array which can be accessed using the “echo” function in the below section.
Example #2
In the below program we will see how to access an element of an array using the echo function.
Code:
<!DOCTYPE html>
<html lang="en">
<head>
<title>Educba- PHP json_decode</title>
</head>
<body>
<?php
$json_string = '[
{
"Companyname": "Educba",
"Director": "Snehal",
"phnumber": "89945954874"
},
{
"Companyname": "Google",
"Director": "Ann",
"phnumber": "9877564694"
}
]';
$x = json_decode($json_string);
echo $x[0]->Companyname;
?>
</body>
</html>
Output:
In the above program, we can see when we have declared a json_string and access any of element in array we use array[index] in any programming language similarly, we write it with echo function and in the above code we have to observe that we have not passed asso_arr parameter in the json_decode() function so to access the element we have to write “echo $x[0]-> Companyname;” and if we set the second parameter to “true” then we have to write “echo $x[0][‘Companyname’];”.
Example #3
In the below, we will see passing an invalid JSON string to the function and try printing the errors also.
Code:
<!DOCTYPE html>
<html lang="en">
<head>
<title>Educba- PHP json_decode</title>
</head>
<body>
<?php
$json_string = '[
{
"Companyname": "Educba"
"Director": "Snehal"
"phnumber": "89945954874"
"Companyname": "Google"
"Director": "Ann"
"phnumber": "9877564694"
}
]';
$x = json_decode($json_string);
echo $x[0]->Companyname;
echo json_last_error();
echo json_last_error_msg();
?>
</body>
</html>
Output:
In the above program, we can see in the variable “json_string” we have passed an invalid JSON data and we are trying to access the object in the above JSON string to PHP object when it is converted using json_decode() function. Then we are even printing json_last_error() and json_last_error_msg() functions which will print about the error information such as “4 syntax error” that is related to the PHP code written in the above example with the screenshot shown above and if we do not want to print any of error messages using the error functions then the output would be “null” that means it will not print anything in the converted objects of PHP as JSON string or data itself is invalid and this can be seen in the below screenshot.
Conclusion
In this article, we conclude that the PHP provides a json_decode() function that is defined as a function for converting or decoding any JSON format string or data into the PHP data type objects as output. In this article we saw how to define or declare the function json_decode() along with its syntax and parameters are explained. Then in the next section, we saw an example of how it will print the arrays if the asso_arr is set to true and false (by default). Then we also saw how to access the array elements and lastly, we also saw what will be the error or what it will print in the output if we have passed an invalid JSON string or data.
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