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永夜

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Analyzing json_decode Failures in PHP 7.4: The Last Error Does Not Mean No Error Occurred

When basename: "collectiontitem", decoding fails

作者：

永夜

在

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Views: 44

1. When basename: “collections”, decoding succeeds. See Figure 1.

When basename: "collections", decoding succeeds
Figure 1

2. When basename: “collectiontitem”, decoding fails. See Figure 2.

When basename: "collectiontitem", decoding fails
Figure 2

3. Check the code implementation for decoding.

PHP

        $result = json_decode($data, true);

        if (json_last_error() !== \JSON_ERROR_NONE) {
            $message = "Invalid json: $data".PHP_EOL;

            if (function_exists('json_last_error_msg')) {
                $message .= ': ' . json_last_error_msg();
            }

            throw new \RuntimeException($message);
        }

4. First, analyze the successful flow and print json_last_error().

PHP

        //var_dump($data);
        $result = json_decode($data, true);
        //var_dump($result);
        var_dump(json_last_error());

        if (json_last_error() !== \JSON_ERROR_NONE) {
            //dd(json_last_error());
            $message = "Invalid json: $data".PHP_EOL;

            if (function_exists('json_last_error_msg')) {
                $message .= ': ' . json_last_error_msg();
            }

            throw new \RuntimeException($message);
        }
Plaintext

int(0)
int(0)
int(0)
int(0)
int(0)
int(0)
int(0)
int(0)
int(0)
int(0)
int(0)
int(0)
int(0)
int(0)
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int(0)

5. Next, analyze the failed flow and print json_last_error(); the value for one of the failures equals 4. See Figure 3.

Next, analyze the failed flow and print json_last_error(); the value for one of the failures equals 4
Figure 3
Plaintext

int(0)
int(0)
int(0)
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int(0)
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int(0)
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int(0)
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int(0)
int(0)
int(0)
int(0)
int(0)
int(4)

6. Print $data and $result when the value is 4.

PHP

        //var_dump($data);
        $result = json_decode($data, true);
        //var_dump($result);
        //var_dump(json_last_error());
        //exit;

        if (json_last_error() !== \JSON_ERROR_NONE) {
            var_dump($data);
            var_dump($result);
            var_dump(json_last_error());
            exit;
            //dd(json_last_error());
            $message = "Invalid json: $data".PHP_EOL;

            if (function_exists('json_last_error_msg')) {
                $message .= ': ' . json_last_error_msg();
            }

            throw new \RuntimeException($message);
        }
Plaintext

string(872) "
{
  "sections": {
    "collection": {
      "type": "collection",
      "settings": {
        "slug": "{{ $CollectionsSlug }}",
        "page": {{ Request::query('page') ?? '1' }}
      }
    },
    "carousel": {
      "type": "carousel",
      "settings": {
        "color_scheme": "inverse",
        "loop": true,
        "autoplay": true,
        "interval": 10,
        "slidesPerView": 6
      },
      "blocks": {
        "slide-1": {
          "type": "slide",
          "settings": {
            "image": "https://cdn.cloudfastin.com/assets/2021/06/4fdfbe61604c5abe7e07746042e532b1.jpg"
          }
        },
        "slide-2": {
          "type": "slide",
          "settings": {
            "image": "https://cdn.cloudfastin.com/assets/2021/06/45077c55aa09821c24aa1610ff7d3830.jpg"
          }
        }
      }
    }
  }
}
"
NULL
int(4)

7. After removing “page”: {{ Request::query(‘page’) ?? ‘1’ }}, parsing succeeds. The final analysis concludes that the cause is a JSON_ERROR_SYNTAX syntax error. See Figure 4.

After removing "page": {{ Request::query('page') ?? '1' }}, parsing succeeds. The final analysis concludes that the cause is a JSON_ERROR_SYNTAX syntax error
Figure 4
PHP

            if (json_last_error() === \JSON_ERROR_SYNTAX) {
                echo 'JSON_ERROR_SYNTAX';
            }

8. To edit $data, replace “page”: {{ Request::query(‘page’) ?? ‘1’ }} with “”page”: {{ Request::query(‘page’) ?? ‘1’ }}””. However, the value type of page is int, and this change turns it into a string. The most fundamental solution is to run the program so that it changes to “page”: 1. See Figure 5.

To edit $data, replace "page": {{ Request::query('page') ?? '1' }} with ""page": {{ Request::query('page') ?? '1' }}"". However, the value type of page is int, and this change turns it into a string. The most fundamental solution is to run the program so that it changes to "page": 1
Figure 5
PHP

        $result = json_decode($data, true);
        var_dump($data);
        var_dump($result);
        var_dump(json_last_error());

        if (json_last_error() !== \JSON_ERROR_NONE) {
            $message = "Invalid json: $data".PHP_EOL;

            if (function_exists('json_last_error_msg')) {
                $message .= ': ' . json_last_error_msg();
            }

            throw new \RuntimeException($message);
        }
Plaintext

string(838) "
{
  "sections": {
    "collection": {
      "type": "collection",
      "settings": {
        "slug": "{{ $CollectionsSlug }}",
        "page": "{{ Request::query('page') ?? '1' }}"
      }
    },
    "carousel": {
      "type": "carousel",
      "settings": {
        "color_scheme": "inverse",
        "loop": true,
        "autoplay": true,
        "interval": 10,
        "slidesPerView": 6
      },
      "blocks": {
        "slide-1": {
          "type": "slide",
          "settings": {
            "image": "https://cdn.cloudfastin.com/assets/2021/06/4fdfbe61604c5abe7e07746042e532b1.jpg"
          }
        },
        "slide-2": {
          "type": "slide",
          "settings": {
            "image": "https://cdn.cloudfastin.com/assets/2021/06/45077c55aa09821c24aa1610ff7d3830.jpg"
          }
        }
      }
    }
  }
}
"
array(1) {
  ["sections"]=>
  array(2) {
    ["collection"]=>
    array(2) {
      ["type"]=>
      string(10) "collection"
      ["settings"]=>
      array(2) {
        ["slug"]=>
        string(22) "{{ $CollectionsSlug }}"
        ["page"]=>
        string(35) "{{ Request::query('page') ?? '1' }}"
      }
    }
    ["carousel"]=>
    array(3) {
      ["type"]=>
      string(8) "carousel"
      ["settings"]=>
      array(5) {
        ["color_scheme"]=>
        string(7) "inverse"
        ["loop"]=>
        bool(true)
        ["autoplay"]=>
        bool(true)
        ["interval"]=>
        int(10)
        ["slidesPerView"]=>
        int(6)
      }
      ["blocks"]=>
      array(2) {
        ["slide-1"]=>
        array(2) {
          ["type"]=>
          string(5) "slide"
          ["settings"]=>
          array(1) {
            ["image"]=>
            string(79) "https://cdn.cloudfastin.com/assets/2021/06/4fdfbe61604c5abe7e07746042e532b1.jpg"
          }
        }
        ["slide-2"]=>
        array(2) {
          ["type"]=>
          string(5) "slide"
          ["settings"]=>
          array(1) {
            ["image"]=>
            string(79) "https://cdn.cloudfastin.com/assets/2021/06/45077c55aa09821c24aa1610ff7d3830.jpg"
          }
        }
      }
    }
  }
}
int(0)

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