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Summary of PHP case-sensitive issues (practical)

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Release: 2016-07-25 08:59:10
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  1. $abc = 'abcd';
  2. echo $abc; //Output 'abcd'
  3. echo $aBc; //No output
  4. echo $ABC; //No output
  5. ?>
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2. Constant names are case-sensitive by default and are usually written in uppercase (But I couldn’t find a configuration item that can change this default, please solve it) example:

  1. define("ABC","Hello World");
  2. echo ABC; //Output Hello World
  3. echo abc; //Output abc
  4. ?>
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3. php.ini configuration item instructions are case sensitive For example, file_uploads = 1 cannot be written as File_uploads = 1

2. Case insensitive 1. Function names, method names, and class names are not case-sensitive, but it is recommended to use the same names as when they were defined. example:

  1. function show(){
  2. echo "Hello World";
  3. }
  4. show(); //Output Hello World Recommended writing method
  5. SHOW(); //Output Hello World
  6. ?> ;
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Example:

  1. class cls{

  2. static function func(){
  3. echo "hello world";
  4. }
  5. }

  6. Cls:: FunC(); //Output hello world

  7. ?>

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2. Magic constants are not case-sensitive, uppercase is recommended Includes: __LINE__, __FILE__, __DIR__, __FUNCTION__, __CLASS__, __METHOD__, __NAMESPACE__. example:

  1. echo __line__; //Output 2
  2. echo __LINE__; //Output 3
  3. ?>
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3. NULL, TRUE, FALSE are not case sensitive example:

  1. $a = null;
  2. $b = NULL;
  3. $c = true;
  4. $d = TRUE;
  5. $e = false;
  6. $f = FALSE;
  7. var_dump($ a == $b); //Output boolean true
  8. var_dump($c == $d); //Output boolean true
  9. var_dump($e == $f); //Output boolean true
  10. ?>
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4. Type coercion, case-insensitive include

  1. $a=1;
  2. var_dump($a); //Output int 1
  3. $b=(STRING)$a;
  4. var_dump($b); //Output string ' 1' (length=1)
  5. $c=(string)$a;
  6. var_dump($c); //Output string '1' (length=1)
  7. ?>
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