应该是这样的:

 function isJson($string)
 {
    // 1. Speed up the checking & prevent exception throw when non string is passed
    if (is_numeric($string) ||
        !is_string($string) ||
        !$string) {
        return false;
    }

    $cleaned_str = trim($string);
    if (!$cleaned_str || !in_array($cleaned_str[0], ['{', '['])) {
        return false;
    }

    // 2. Actual checking
    $str = json_decode($string);
    return (json_last_error() == JSON_ERROR_NONE) && $str && $str != $string;
}

单元测试

public function testIsJson()
{
    $non_json_values = [
        "12",
        0,
        1,
        12,
        -1,
        '',
        null,
        0.1,
        '.',
        "''",
        true,
        false,
        [],
        '""',
        '[]',
        '   {',
        '   [',
    ];

   $json_values = [
        '{}',
        '{"foo": "bar"}',
        '[{}]',
        '  {}',
        ' {}  '
    ];

   foreach ($non_json_values as $non_json_value) {
        $is_json = isJson($non_json_value);
        $this->assertFalse($is_json);
    }

    foreach ($json_values as $json_value) {
        $is_json = isJson($json_value);
        $this->assertTrue($is_json);
    }
}

简单的方法是检查json结果..

$result = @json_decode($json,true);
    if (is_array($result)) {
        echo 'JSON is valid';
    }else{
        echo 'JSON is not valid';
    }

嗨，这是我的库中的一个小片段，在第一个条件下，我只是检查数据是否为json，然后返回它，如果正确解码，请注意substr的使用性能(我还没有看到任何json文件不以{或[开始

$input=trim($input);
if ((substr($input, 0, 1) == '{' && substr($input, -1) == '}') or (substr($input, 0, 1) == '[' && substr($input, -1) == ']')) {
    $output = json_decode($input, 1);
    if (in_array(gettype($output),['object','array'])) {
        #then it's definitely JSON
    }
}

在GuzzleHttp:

/**
 * Wrapper for json_decode that throws when an error occurs.
 *
 * @param string $json    JSON data to parse
 * @param bool $assoc     When true, returned objects will be converted
 *                        into associative arrays.
 * @param int    $depth   User specified recursion depth.
 * @param int    $options Bitmask of JSON decode options.
 *
 * @return mixed
 * @throws \InvalidArgumentException if the JSON cannot be decoded.
 * @link http://www.php.net/manual/en/function.json-decode.php
 */
function json_decode($json, $assoc = false, $depth = 512, $options = 0)
{
    $data = \json_decode($json, $assoc, $depth, $options);
    if (JSON_ERROR_NONE !== json_last_error()) {
        throw new \InvalidArgumentException(
            'json_decode error: ' . json_last_error_msg());
    }

    return $data;
}

/**
 * Wrapper for JSON encoding that throws when an error occurs.
 *
 * @param mixed $value   The value being encoded
 * @param int    $options JSON encode option bitmask
 * @param int    $depth   Set the maximum depth. Must be greater than zero.
 *
 * @return string
 * @throws \InvalidArgumentException if the JSON cannot be encoded.
 * @link http://www.php.net/manual/en/function.json-encode.php
 */
function json_encode($value, $options = 0, $depth = 512)
{
    $json = \json_encode($value, $options, $depth);
    if (JSON_ERROR_NONE !== json_last_error()) {
        throw new \InvalidArgumentException(
            'json_encode error: ' . json_last_error_msg());
    }

    return $json;
}

对亨里克的回答做一个简单的修改，以触及最需要的可能性。

(包括“{}和[]”)

function isValidJson($string) {
    json_decode($string);
    if(json_last_error() == JSON_ERROR_NONE) {

        if( $string[0] == "{" || $string[0] == "[" ) { 
            $first = $string [0];

            if( substr($string, -1) == "}" || substr($string, -1) == "]" ) {
                $last = substr($string, -1);

                if($first == "{" && $last == "}"){
                    return true;
                }

                if($first == "[" && $last == "]"){
                    return true;
                }

                return false;

            }
            return false;
        }

        return false;
    }

    return false;

}

你真正需要做的就是…

if (is_object(json_decode($MyJSONArray))) 
{ 
    ... do something ...
}

这个请求甚至不需要一个单独的函数。只需将is_object包装在json_decode周围，然后继续。似乎这个解决方案让人们花了太多心思。