Mysql not equal full#However, to declare a floating point number, one must always use a full stop otherwhise the code would be locale dependent (imagine the nightmare): When PHP converts a float to a string, the decimal separator used depends on the current locale conventions. No "conversions".Īnd please mind the Big and Little endian boys.Īs "m dot lebkowski+php at gmail dot com" ( ) noted 9 comments below : In C++ you can access the same 32/64 data as either float/double or 32/64 bit integer. Using pack/unpack you use processor's encoding, which is always correct. I get 0 both for 32-bit and 64-bit numbers.īut, please don't use your own "functions" to "convert" from float to binary and vice versa. So if you REALLY need to be sure to have the string correctly formatted, use number_format() to do it! The problem persists, if you use the "." operator instead of evaluating the variable in the string. Similar problems could arise anywhere else (SQL, any string used as code somewhere else). JavaScript won't state an error, additional arguments are discarded without notice, but the function doBar(a) would get 0 as parameter. Which is obviously a different call to the function. On most systems, this would print:īut when for example a user from Germany arrives, it would be different: This would result in a different result for users with some locales. The float is actually formatted according to the browser's locale setting, which means that "0.23" will result in "0,23". That's also titled "Why don’t my numbers add up?"īe careful when using float values in strings that are used as code later, for example when generating JavaScript code or SQL statements. Necessary, the arbitrary precision math functionsįor a "simple" explanation, see the » floating point guide So never trust floating number results to the last digit, and do not compareįloating point numbers directly for equality. Since the internal representation will be something like Results: for example, floor((0.1+0.7)*10) will usually Hence, they cannot be converted into their internal binaryĬounterparts without a small loss of precision. Point numbers in base 2, which is used internally, no matter the size of Non elementary arithmetic operations may give larger errors, and, of course,Įrror propagation must be considered when several operations areĪdditionally, rational numbers that are exactly representable as floatingĠ.7, do not have an exact representation as floating Give a maximum relative error due to rounding in the order of 1.11e-16. System, PHP typically uses the IEEE 754 double precision format, which will Mysql not equal archive#Getting Started Introduction A simple tutorial Language Reference Basic syntax Types Variables Constants Expressions Operators Control Structures Functions Classes and Objects Namespaces Enumerations Errors Exceptions Fibers Generators Attributes References Explained Predefined Variables Predefined Exceptions Predefined Interfaces and Classes Context options and parameters Supported Protocols and Wrappers Security Introduction General considerations Installed as CGI binary Installed as an Apache module Session Security Filesystem Security Database Security Error Reporting User Submitted Data Hiding PHP Keeping Current Features HTTP authentication with PHP Cookies Sessions Dealing with XForms Handling file uploads Using remote files Connection handling Persistent Database Connections Command line usage Garbage Collection DTrace Dynamic Tracing Function Reference Affecting PHP's Behaviour Audio Formats Manipulation Authentication Services Command Line Specific Extensions Compression and Archive Extensions Cryptography Extensions Database Extensions Date and Time Related Extensions File System Related Extensions Human Language and Character Encoding Support Image Processing and Generation Mail Related Extensions Mathematical Extensions Non-Text MIME Output Process Control Extensions Other Basic Extensions Other Services Search Engine Extensions Server Specific Extensions Session Extensions Text Processing Variable and Type Related Extensions Web Services Windows Only Extensions XML Manipulation GUI Extensions Keyboard Shortcuts ? This help j Next menu item k Previous menu item g p Previous man page g n Next man page G Scroll to bottom g g Scroll to top g h Goto homepage g s Goto searchįloating point numbers have limited precision.
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