Psalm plugin to work with `sprintf`, `printf`, `sscanf` and `fscanf`.

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1.4.0 2022-12-10 15:57 UTC


Build Status

This plugin provides additional checks to the built-in sprintf, printf, sscanf and fscanf function usage.


Require composer dev-dependency

composer require --dev boesing/psalm-plugin-stringf

Run Psalm-Plugin Binary

vendor/bin/psalm-plugin enable boesing/psalm-plugin-stringf


  • Parses sprintf and printf arguments to verify if the number of passed arguments matches the amount of specifiers
  • Verifies if the return value of sprintf might be a non-empty-string
  • Verifies possibly invalid argument of sprintf and printf (experimental)
  • Verifies unnecessary function calls of sprintf and printf (experimental)


This plugin also provides experimental features.

Experimental features can be enabled by extending the plugin configuration as follows:

<?xml version="1.0"?>
        <pluginClass class="Boesing\PsalmPluginStringf\Plugin">

Report Possibly Invalid Argument for Specifier

<pluginClass class="Boesing\PsalmPluginStringf\Plugin">
        <ReportPossiblyInvalidArgumentForSpecifier allowIntegerForString="yes" />

The ReportPossiblyInvalidArgumentForSpecifier experimental feature will report PossiblyInvalidArgument errors for arguments used with sprintf or printf. Here are some examples:

printf('%s', 1);
PossiblyInvalidArgument: Argument 1 inferred as "int" does not match (any of) the suggested type(s) "string"
printf('%d', 'foo');
PossiblyInvalidArgument: Argument 1 inferred as "string" does not match (any of) the suggested type(s) "float\|int\|numeric-string"

Report Unnecessary Function Calls

<pluginClass class="Boesing\PsalmPluginStringf\Plugin">

The ReportUnnecessaryFunctionCalls experimental feature will report UnnecessaryFunctionCall errors for function calls to sprintf or printf which can be omitted. Here are some examples:

printf('Some text without any placeholder');
sprintf('Some text without any placeholder');
UnnecessaryFunctionCall: Function call is unnecessary as there is no placeholder within the template.

Release Versioning Disclaimer

This plugin won't follow semantic versioning even tho the version numbers state to be semantic versioning compliant. The source code of this plugin is not meant to used like library code and therefore MUST be treated as internal code.

  • This package will raise dependency requirements whenever necessary.
  • If there is a new major version of psalm, this plugin MAY migrate to that version but won't be early adopter.
  • If there is a new PHP minor/major version which is not supported by this library, this library MAY migrate to that version but won't be early adopter.

So to summarize: If your project depends on the latest shiny versions of either Psalm or PHP, this plugin is not for you. If you can live with that, feel free to install. Demands in any way will be either ignored or handled whenever I feel I want to spend time on it.