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    1: 1. strrpos() and strripos() now use the entire string as a needle.  Be aware
    2:    that the existing scripts may no longer work as you expect.
    3: 
    4:    EX :
    5:    <?php
    6:    var_dump(strrpos("ABCDEF","DEF"));
    7:    var_dump(strrpos("ABCDEF","DAF"));
    8:    ?>
    9: 
   10:    Will give you different results. The former returns 3 while the latter
   11:    returns false rather than the position of the last occurrence of 'D'.
   12:    The same applies to strripos().
   13: 
   14: 2. Illegal use of string offsets causes E_ERROR instead of E_WARNING.
   15: 
   16:    EX :
   17:    <?php
   18:    $a = "foo";
   19:    unset($a[0][1][2]);
   20:    ?>
   21: 
   22:    Fatal error: Cannot use string offset as an array in ... on line 1
   23: 
   24: 3. array_merge() was changed to accept only arrays. If a non-array variable is
   25:    passed, a E_WARNING will be thrown for every such parameter. Be careful
   26:    because your code may start emitting E_WARNING out of the blue.
   27: 
   28: 4. Be careful when porting from ext/mysql to ext/mysqli. The following
   29:    functions return NULL when no more data is available in the result set
   30:    (ext/mysql's functions return FALSE).
   31: 
   32:     - mysqli_fetch_row()
   33:     - mysqli_fetch_array()
   34:     - mysqli_fetch_assoc()
   35: 
   36: 5. PATH_TRANSLATED server variable is no longer set implicitly under
   37:    Apache2 SAPI in contrast to the situation in PHP 4, where it is set to the
   38:    same value as the SCRIPT_FILENAME server variable when it is not populated
   39:    by Apache.  This change was made to comply with the CGI specification.
   40:    Please refer to bug #23610 for further information.
   41: 
   42: 6. Starting PHP 5.0.0 the T_ML_CONSTANT constant is no longer defined by the
   43:    ext/tokenizer extension. If error_reporting is set to E_ALL notices will
   44:    be produced. Instead of T_ML_CONSTANT for /* */ the T_COMMENT constant 
   45:    is used, thus both // and /* */ are resolved as the T_COMMENT constant.
   46:    However the PHPDoc style comments /** */ ,which starting PHP 5 are parsed
   47:    by PHP, are recongnized as T_DOC_COMMENT.
   48: 
   49: 7. $_SERVER should be populated with argc and argv if variables_order
   50:    includes "S".  If you have specifically configured your system to not
   51:    create $_SERVER, then of course it shouldn't be there.  The change was to
   52:    always make argc and argv available in the CLI version regardless of the
   53:    variables_order setting.  As in, the CLI version will now always populate
   54:    the global $argc and $argv variables.
   55: 
   56: 8. In some cases classes must be declared before used. It only happens only
   57:    if some of the new features of PHP 5 are used. Otherwise the behaviour is
   58:    the old.
   59:    Example 1 (works with no errors):
   60:    <?php
   61:    $a = new a();
   62:    class a {
   63:    }
   64:    ?>
   65:  
   66:    Example 2 (throws an error):
   67:    <?php 
   68:    $a = new a();
   69:    interface b{
   70:    }
   71:    class a implements b {
   72:    } 
   73:    ?>
   74: 
   75:    Output (example 2) :
   76:    Fatal error: Class 'a' not found in /tmp/cl.php on line 2
   77: 
   78: 9. get_class() starting PHP 5 returns the name of the class as it was
   79:    declared which may lead to problems in older scripts that rely on
   80:    the previous behaviour - the class name is lowercased. Expect the
   81:    same behaviour from get_parent_class() when applicable.
   82:    Example :
   83:    <?php
   84:    class FooBar {
   85:    }
   86:    class ExtFooBar extends FooBar{}
   87:    $a = new FooBar();
   88:    var_dump(get_class($a), get_parent_class($a));
   89:    ?>
   90: 
   91:    Output (PHP 4):
   92:    string(6) "foobar"
   93:    string(9) "extfoobar"
   94: 
   95:    Output (PHP 5):
   96:    string(6) "FooBar"
   97:    string(9) "ExtFooBar"
   98:    ----------------------------------------------------------------------
   99:    Example code that will break :
  100:    //....
  101:    function someMethod($p) {
  102:      if (get_class($p) != 'helpingclass') {
  103:        return FALSE;
  104:      }
  105:      //...
  106:    }
  107:    //...
  108:    Possible solution is to search for get_class() and get_parent_class() in
  109:    all your scripts and use strtolower().
  110: 
  111: 10. get_class_methods() returns the names of the methods of a class as they
  112:    declared. In PHP4 the names are all lowercased.
  113:    Example code :
  114:    <?php
  115:    class Foo{
  116:      function doFoo(){}
  117:      function hasFoo(){}
  118:    }
  119:    var_dump(get_class_methods("Foo")); 
  120:    ?>
  121:    Output (PHP4):
  122:    array(2) {
  123:      [0]=>
  124:      string(5) "dofoo"
  125:      [1]=>
  126:      string(6) "hasfoo"
  127:    }
  128:    Output (PHP5):
  129:    array(2) {
  130:      [0]=>
  131:      string(5) "doFoo"
  132:      [1]=>
  133:      string(6) "hasFoo"
  134:    }
  135: 
  136: 11. Assignment $this is impossible. Starting PHP 5.0.0 $this has special
  137:     meaning in class methods and is recognized by the PHP parser. The latter
  138:     will generate a parse error when assignment to $this is found
  139:     Example code :
  140:     <?php
  141:     class Foo {
  142:       function assignNew($obj) {
  143:         $this = $obj;
  144:       }
  145:     }
  146:     $a = new Foo();
  147:     $b = new Foo();
  148:     $a->assignNew($b);
  149:     echo "I was executed\n";
  150:     ?>
  151:     Output (PHP 4):
  152:     I was executed
  153:     Output (PHP 5):
  154:     PHP Fatal error:  Cannot re-assign $this in /tmp/this_ex.php on line 4
  155: