PHP 7 Incompatibility Error

FILE: ../wp-content/plugins/wp-file-manager/file_folder_manager.php
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FOUND 1 ERROR AFFECTING 1 LINE
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131 | ERROR | Extension ‘mysql_’ is deprecated since PHP 5.5 and removed since PHP 7.0 – use mysqli instead.
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FILE: ../wp-content/plugins/wp-file-manager/lib/php/elFinder.class.php
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FOUND 0 ERRORS AND 6 WARNINGS AFFECTING 6 LINES
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463 | WARNING | INI directive ‘iconv.internal_encoding’ is deprecated since PHP 5.6.
464 | WARNING | INI directive ‘iconv.internal_encoding’ is deprecated since PHP 5.6.
466 | WARNING | INI directive ‘mbstring.internal_encoding’ is deprecated since PHP 5.6.
467 | WARNING | INI directive ‘mbstring.internal_encoding’ is deprecated since PHP 5.6.
2198 | WARNING | INI directive ‘safe_mode’ is deprecated since PHP 5.3 and removed since PHP 5.4.
4248 | WARNING | INI directive ‘safe_mode’ is deprecated since PHP 5.3 and removed since PHP 5.4.
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Not too worried about about the warnings, but how can the Error be resolved?

Thanks