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| rfc:trailing_whitespace_numerics [2019/02/07 01:38] – TBDs ajf | rfc:trailing_whitespace_numerics [2019/03/04 22:14] – ajf |
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| [[rfc:invalid_strings_in_arithmetic|Since PHP 7.1]], most parts of PHP that perform string to number conversions use the same definitions of numeric strings, and differ only in the types of errors that non-well-formed and non-numeric strings produce. According to those definitions: | [[rfc:invalid_strings_in_arithmetic|Since PHP 7.1]], most parts of PHP that perform string to number conversions use the same definitions of numeric strings, and differ only in the types of errors that non-well-formed and non-numeric strings produce. According to those definitions: |
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| * A //well-formed// numeric string contains a number optionally preceded by whitespace. For example, <php>"123"</php> is well-formed (just a number), and <php" 1.23e2"</php> is also well-formed (a number preceded by whitespace). | * A //well-formed// numeric string contains a number optionally preceded by whitespace. For example, <php>"123"</php> is well-formed (just a number), and <php>" 1.23e2"</php> is also well-formed (a number preceded by whitespace). |
| * A //non-well-formed// numeric string is any string beginning with a well-formed numeric string but followed by other characters, notably including whitespace. For example, <php>"1.23e2abc"</php> is non-well-formed (a number followed by unrelated letters), and <php>" 1.23e2 "</php> (a number both preceded and followed by whitespace) is also non-well-formed. | * A //non-well-formed// numeric string is any string beginning with a well-formed numeric string but followed by other characters, notably including whitespace. For example, <php>"1.23e2abc"</php> is non-well-formed (a number followed by unrelated letters), and <php>" 1.23e2 "</php> (a number both preceded and followed by whitespace) is also non-well-formed. |
| * A //non-numeric// string is a string that is neither a well-formed nor a non-well-formed numeric string. For example, <php>"abc1.23e2"</php> is non-numeric (it doesn't start with a number, nor does it start with whitespace followed by a number). | * A //non-numeric// string is a string that is neither a well-formed nor a non-well-formed numeric string. For example, <php>"abc1.23e2"</php> is non-numeric (it doesn't start with a number, nor does it start with whitespace followed by a number). |
| The hope is that the backwards compatibility impact would be limited by Part 1's acceptance of trailing whitespace, since that would prevent a large category of currently non-well-formed strings from being affected. | The hope is that the backwards compatibility impact would be limited by Part 1's acceptance of trailing whitespace, since that would prevent a large category of currently non-well-formed strings from being affected. |
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| In order to prepare for the backwards-compatibility break in the following major version, the “A non well formed numeric value encountered” notice (where currently produced) should be changed in the PHP 7.x (currently PHP 7.4) to mention that this behaviour is deprecated, i.e. ”A non well formed numeric value encountered (non well formed numeric values are deprecated and will be considered non-numeric in PHP 8.0)”. | In order to prepare for the backwards-compatibility break in the following major version, the “A non well formed numeric value encountered” notice (where currently produced) should be changed in the next PHP 7.x (currently PHP 7.4) to mention that this behaviour is deprecated, i.e. ”A non well formed numeric value encountered (non well formed numeric values are deprecated and will be considered non-numeric in PHP 8.0)”. |
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| For the PHP interpreter, this change would be accomplished by modifying the ''is_numeric_string'' C function (and its variants) in the Zend Engine. This would therefore affect PHP features which make use of this function, including: | For the PHP interpreter, this change would be accomplished by modifying the ''is_numeric_string'' C function (and its variants) in the Zend Engine. This would therefore affect PHP features which make use of this function, including: |
| It would not affect the following features, since they already treat non-well-formed numeric strings strictly: | It would not affect the following features, since they already treat non-well-formed numeric strings strictly: |
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| * The comparison operators | |
| * The <php>\is_numeric</php> function | * The <php>\is_numeric</php> function |
| * The <php>++</php> and <php>--</php> operators | * The <php>++</php> and <php>--</php> operators |
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| | TBD: comparison operators |
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| TBD: what about explicit conversions, though? | TBD: what about explicit conversions, though? |