(PHP 8 >= 8.3.0)
json_validate — Checks if a string contains valid JSON
Returns whether the given string is syntactically valid JSON.
If json_validate() returns true, json_decode()
will successfully decode the given string when using the same
depth and flags.
If json_validate() returns false, the cause
can be retrieved using json_last_error() and
json_last_error_msg().
json_validate() uses less memory than json_decode() if the decoded JSON payload is not used, because it does not need to build the array or object structure containing the payload.
Calling json_validate() immediately before json_decode() will unnecessarily parse the string twice, as json_decode() implicitly performs validation during decoding.
json_validate() should therefore only be used if the decode JSON payload is not immediately used and knowing whether the string contains valid JSON is needed.
jsonThe string to validate.
This function only works with UTF-8 encoded strings.
Note:
PHP implements a superset of JSON as specified in the original » RFC 7159.
depth
Maximum nesting depth of the structure being decoded.
The value must be greater than 0,
and less than or equal to 2147483647.
flags
Currently only
JSON_INVALID_UTF8_IGNORE
is accepted.
Returns true if the given string is syntactically valid JSON, otherwise
returns false.
If depth is outside the allowed range,
a ValueError is thrown.
If flags is not a valid flag,
a ValueError is thrown.
Example #1 json_validate() examples
<?php
var_dump(json_validate('{ "test": { "foo": "bar" } }'));
var_dump(json_validate('{ "": "": "" } }'));
?>The above example will output:
bool(true) bool(false)
---------------- PHP < 8.3 ----------------
function json_validate(string $string): bool {
json_decode($string);
return json_last_error() === JSON_ERROR_NONE;
}
var_dump(json_validate('{ "test": { "foo": "bar" } }')); // true
---------------- PHP >= 8.3 ----------------
var_dump(json_validate('{ "test": { "foo": "bar" } }')); // true
Note: code from https://www.php.net/releases/8.3/en.php
Building upon Allan R.'s initial idea, I've developed an improved version of the json_validate function for those using PHP 8.2 and earlier versions. This function emulates the functionality introduced in PHP 8.3, providing an effective way to validate JSON strings in earlier PHP versions.
```php
if (!function_exists('json_validate')) {
/**
* Validates a JSON string.
*
* @param string $json The JSON string to validate.
* @param int $depth Maximum depth. Must be greater than zero.
* @param int $flags Bitmask of JSON decode options.
* @return bool Returns true if the string is a valid JSON, otherwise false.
*/
function json_validate($json, $depth = 512, $flags = 0) {
if (!is_string($json)) {
return false;
}
try {
json_decode($json, false, $depth, $flags | JSON_THROW_ON_ERROR);
return true;
} catch (\JsonException $e) {
return false;
}
}
}
```
Key Improvements:
- String Check: Added a validation to ensure the input is a string.
- Error Handling: Utilizes try-catch to effectively catch and handle JsonException.
- Backward Compatibility: Safely integrable in older PHP versions, automatically deferring to native functionality in PHP 8.3+.
Pre PHP 8.3, and future compatible, function/wrapper
---
if(!function_exists("json_validate")) {
function json_validate() {
try {
json_decode($json, JSON_THROW_ON_ERROR);
return true;
} catch(\JsonException) {
return false;
}
}
}
---
An issue with simply relying on json_last_error() == JSON_ERROR_NONE is if you have an error handler that catches errors or notices and throws them instead as fx. \ErrorException
That would cause a call to json_decode(); to throw an exception exiting the scope of the function.
